I have looked into some homebrews for this as a PC and NPC, but only found 1 decent creation here https://www.dandwiki.com/wiki/Hound_Archon_(5e_Race)  and other docs for 3.5 pathfinder. Right now I am basically reskinning the tabaxi stat blocks and racial features, but the DM said he will allow homebrew races (as this will be a long campaign and 2 others are interested in non AL race options) if it is balanced enough. 

Any thoughts or suggestions on how this should be altered? Ability modifiers, racial features?

pg 23 of 3.5e planar handbook has a hound archon player race, the wiki version is not a great version of it, the 3.5e version Is level based so needs heavy, heavy tweaking for a transfer to 5e but for reference was:

Starting Languages: Celestial, Draconic, Infernal, Sylvan (not: cannot speak cmmon)

Size Medium

Speed 40ft

HIT DICE: d8 (gain 1d8 at first level, and a further d8 at levels 2, 3, 5, 7, 9 to make a total of 6d8 at 9th level)

IMPORTANT NOTE: they do not get any ability score adjustment at 1st level, they come in at various levels

lvl 1: Bonus Feat, Darkvision 60ft, Subtype archon/extra planar/lawful, natural attacks: bite (1d6) & slam (1d3), +2 Natural Armour, resistance to electricity 5, +4 bonus to save vs poison,

so converting that lot over would give you: Bonus Feat as per Variant Human, Darkvison 60ft, Subtype Celestial, Natural Attacks: Bite 1d6 Piercing & Slam 1d3 Bludgeoning, Base AC = 12 +Dex, Resistance to Lightning & poison damage, Advantage on Saves to resist being posioned.

lvl 2: +2 Cons, Detect Evil @ Will & Message x3/day (but no reference to spell casting ability so assumeing wisdom based on their tongues ability), +3 Natural Armour (replaces previous +2 bonus)

So that converts over to: +2 Cons, Detect Evil & Good @ Will without spending a spell slot (wisdom spell casting mod?), Message as per Cantrip @ Will (I can't see the point in limiting it to x3/LR), Base AC = 13 +Dex

lvl 3: Bonus Feat, Aid x3/day, Conitinual Flame x3/day

So that converts over as is with the only adjustment needing to be Aid x3 per long rest & Continual Flame x3 per long rest

lvl 4: +2 Str, Resistance to LIghtning 10, Tongues (as if cast by a cleric), +4 Natural Armour

So that converts to: +2 Str, Always deemed to be under the effects of the Tongues spell unless the hound archon chooses not to be but it requires an action to reactive if it is switched off or dispelled. Base AC = 14 +Dex

lvl 5: Change Shape, Scent, +5 Natural Armour.

So that converts to: Can polymorph into any Canine shape of large size or smaller @ Will, Scent: Gain Advantage on perception rolls involving smell (might also extend to certain survival or investigation rolls), Base AC = 15 +Dex

lvl 6:Bite 1d8, slam 1d4, +6 Natural AC, Message @ Will

so that converts to: Natural attacks: Bite now deals 1d8 Piericing, Slame 1d4 Bludgeoning, Base AC = 16 +Dex

lvl 7: Aura od Meance (save or get -2 to attack, AC and saving throws for 24 hours or until you hit the hound archon), Resistance to Electricity 20, +7 Natural Armour

so that converts to: Aura of Meance: Wisdom save (DC 8 + 1/2 prof bonus + cha mod) or become frightened as per condition  for 24 hours or until you hit the hound archon,  Base AC = 17 +Dex

lvl 8: Greater Teleport 1/day, Spell Resistance 13, +8 Natural Armour

so that converts ot: Can cast Teleport x1/LR without need to expend a spell slot, Advantage on saving throws vs spells, Base AC = 18 +Dex

lvl 9: Bonus Feat, +2 Cha, Damage reduction 5/evil, Aid @ Will, Conitnual Flame @ Will.Spell Restance 14

so that converts to: +2 Cha, Damage Restance to Bludgeoning, Slashing and Piericng unless form an evil source/alignment, Aid & Continual Flame now both at will

lvl 10: +2 Wis, Immune to Electricity & Petrification, +9 Natural Amrour, spell Resistance 15

so that converts to: +2 Wis, Immune to lIghtning damage, Immune to the Petrification Condition, Base AC = 19 +Dex

final level 11: +2 Str, damage rediuction 10/evil, greter teleport @ will, Magic Circle against evil, spell resistance 16

so that changes to: +2 Str, Damage reduction remains unchanged form above, Teleport now becomes at will, can now also cast Magic Circle @ will as alevel 3 spell without expending a spell slot

*****

I don't think it would be completely infeasible for player in 5e but as a DM I would say it also counts as a class so when you gain xp you have to choose whether to level up your hound archon abilities or take a character class and Hound Archon has to be the first level you start with, not sure about the tleporting aspect either, I think I;d either nerf it to teleportation circle and limit it to x1 per LR or remove it completely and the natual armour ability might need ot be switch to soemthing more akin to the Barbarian ro Monk unarmoured defese so no stacking with normal armour.

The spell casting ability is a bit ambuguous as well as some mention charisma based and other as if the spell were cast by a cleric so could also be wisdom based and all spells would be cast at their lowest level.

Thank you for this! I think treating it as a race and/or class in the sense that I would need to choose either the hound archon class or my chosen class would be a tad overwhelming (personally). In terms of base stats I like your ideas of tweaking the teleport and natural armor. Maybe this would be a good starting block?

Canine-headed celestial defenders of the innocent and the helpless against evil.
Ability Score Increase. Your Strength score increases by 2 and your Wisdom score increases by 1.
Age. Hound Archons do not age.
Alignment. Favoring lawful good alignment as they originate on the Upper Plane, though it is not completely unheard of to be turned lawful evil through fell magic.
Size. Your size is Medium.
Speed. Your base walking speed is 40 feet.
Darkvision. You can see in dim light within 60 feet of you as if it were bright light, and in darkness as if it were dim light. You can't discern color in darkness, only shades of gray.
Shapechange. You can use your action to shape change into a jackal (MM p. 331), mastiff (MM p. 332) or wolf (MM p. 341). Use the rules for the druid's wild shape feature, (PHB p.66) with the exception that this effect has a maximum duration of one hour. You can use this feature once per short or long rest.
Natural weapons. You have fangs and sharp claws. Your unarmed strike deals 1d4 piercing damage.
Magic of the Seven Heavens. You know the light cantrip. When you reach 3rd level, you can cast the see invisbility spell once. When you reach 5th level, you can cast the prayer for healing spell once. You regain the use of these spells when you finish a long rest.
Celestial. Your creature type is both humanoid and celestial.
Aura of Menace. A righteous aura surrounds archons that fight or get angry. Any hostile creature within a 20-foot radius of an archon must succeed on wisdom saving throw or become frightened for 24 hours or until the archon is damaged.
Languages. You can speak, read and write Common, and Celestial

This might be a bit much and if so what should be pulled and what should stay (or be tweaked). 

The main problem you are going to have is that Hound Archon's are full Celestial and this is more like a half breed (assimar/tiefling), if you dont have the race build like a class then your alternative may well be racial feats.

On what you 've put above it is a good starting point but I would keep the spell casting to be in line with the 3.5e verision (not sure if there is a published 5e hound archon), so have Message @ Will Aid x1/LR, Tongues x1/LR. I'd probably keep the shape change abilityt o any non-magical canine form witht he Beast type, so dog, mastiff, jackal, wolf are ok but no Fey or Monstrosities such as death dog, blink dog etc.

You could have a little bit of fluff about the Hound Archons being displaced or sent on a quest to prove themselves (hence whiy their power is dimiinished).

Then you can  have racial feats such as:

Hound Archn Spell Casting 1: You can now cast Aid x3/LR and COntinual Flame x3/LR and your TOngues spell is alwasy activate unless you choose for it not to be or unless it is dispelled. If you deactivate TOngues or it is Dispelled you can use an Action to reactivate it.

Hound Archon Spell Casting 2: Requires Hound Archon Spell Casting 1. Gain the ability to cast Teleportation Circle x1/LR without expending a spell slot.

Hound Archon Spell Casting 3: Requires Hound Archon Spell Casting 1 & 2. Can now cast Teleport x1/LR and can cast Magic Circle a number of times per LR equal to Wisdom Modifier without expending a spell slot..

Hound Archon Resistances 1: Gain Resistance to Lightning and Posion Damage and have advantage on saves vs Posion. Also gain +1 Constitution. (This is really just an ameneded version of the Tiefling Infernal Constitution Feat form XGtE)

Hound Archon resistances 2: Requires Hound Archon resistances 1. Gain Immunity to Lightning damage and Petrification and gain resistance to Bludgeoning, Slashing and Piercing damage from non-magical weapons unless weilded by Evil creatures.

Hound Archon Hide: Gain Natural Armour, AC now calculated as 10+ Wis Bonus +Dex, this does not stack with AC from armour or shields its either/or as per the Monk unarmoured defence abilitiy. Your Bite attack now deals 1d6 piercing damage and your claw attacks now deal 1d4 slashing damage. (This is really just an ameneded version of the Dragon Hide Dragonborn Feat form XGtE)

If you manage to get them all then you've pretty much got the full Hound Archon special abilites but I think the only way you'll get ehm all is to have Fighter as a class which would also make sense given they are a martial kind of celestial. You're ability scores won't match up completely as the Hound Archon in 3.5e effectively got +4 Str, +2 COns, +2 wWis and +2 Cha but I don't think you'll miss it to much given everything else you can get, plus if you went fighter for a class you can actually get 8 ASi/Feat options so you could get 2 ability score increases in addition to the racial feats above.

I really like your idea for spell casting and resistance progression, I honestly don't think there is any other way to do this and have an authentic Hound Archon from 3.5. Anything else will just feel/be a diluted or revamped form of it (also ok). I'm torn, but this has been incredibly helpful, luckily I have a few more days to get this flushed out and hopefully combine the two. Thank you for your time!

 I too am working on a hound archon race.   I'm having trouble balancing it out as well.  Looking at the homebrews on d&dbeyond, this thread, and some other sources, I've come to the conclusion that progressive abilities/spell casting/resistances/etc. may be the only way to make it work as long as it isn't on a celestial plane.  Now top that with character classes.  It still seems overpowered to me.  It may be that I've been staring at it too long.   If progression is key, then what goes at which levels?  What gets stripped away?  These are the details I'm working with, including stuff that Rob76 used in in this thread:

Hound Archon

Celestial Outsider

Alignment Always Good. Usually Lawful, but not necessarily.

Lifespan: Hound Archons are occasionally created/evolved from the souls of departed canine (wolf/fox/dog/coyote/jackal) that are found to be worthy by a good-aligned deity. When a hound archon is "born" it'll quickly grow to physical maturity by the age of 5. After reaching physical maturity they age very slowly on the material plane, living up to 300 years old. When a hound archon "dies" it returns to the Celestial Plane and cannot return to the Material Plane. Immortal Origin: Your spirit is native to the Astral Sea, so you are considered an immortal creature for the purpose of effects that relate to creature origin.

Size: Medium. 4 ft tall to 7 foot tall, depending on "breed".

Speed: base walking speed is 40 feet

Languages: Celestial and one other language from this list: Common, Draconic, Dwarven, Elven, Gnomish, Halfling, Infernal, Sylvan.

Vision: Darkvision: You can see in dim light within 60 feet of you as if it were bright light, and in darkness as if it were dim light. You can't discern color in any lighting, only shades of grey.

Ability Scores: +2 Strength, +2 to either Constitution, Wisdom, or Charisma (depending on "breed").

Favored classes (in descending order): Paladin, Cleric, Druid, Ranger, Zealot Barbarian, (Religious) Lore Bard.

Natural Weapons: Bite (1d8+str), Claws (1d4+str modifier per hand), and slam (1d4). A hound archon’s natural weapons, as well as any weapons it wields, are treated as good-aligned and lawful-aligned for the purpose of overcoming damage reduction.

Celestial Resistance You have resistance to necrotic damage and radiant damage.

Magic of the Seven Heavens: You know the light and message cantrips. When you reach 3rd level, you can cast the invisibility spell once per long rest. When you reach 5th level, you can cast the prayer for healing spell once per long rest.
.........
Damage Reduction 10/evil

Spell Resistance equal to 16 + class levels.

Racial Hit Dice: Level adjustment +5/A hound archon begins with six levels of outsider, which provide 6d8 Hit Dice, a base attack bonus of +6, and base saving throw bonuses of Fort +5, Ref +5, and Will +5.

Racial Skills: A hound archon’s class skills are Athletics, Stealth, Perception, and Religion. Advantage on constitution saving throws. Keen Senses: Advantages to perception and investigation checks involving sight and/or smell and/or hearing. (certain "breeds" get higher smell checks). In addition, you can use your bonus action to roll perception and attempt and sniff out the location of an invisible or hiding creature, the DC for this is the creatures CR minus your proficiency bonus. The creature must have a scent for this feature to work. Natural Intimidation: Advantage on intimidation checks at 7th level. *While in canine form, a hound archon gains a +4 circumstance bonus on Hide and Survival checks.

Aura of Menace: A righteous aura surrounds hound archons that fight or get angry. Any hostile creature within a 20-foot radius of a hound archon must succeed on a Will save (DC 16) to resist its effects. The save DC is Charisma-based, and includes a +2 racial bonus. Those who fail become frightened for 24 hours, take a –2 penalty on attacks, AC, and saves for 24 hours or until they successfully hit the hound archon that generated the aura. A creature that has resisted or broken the effect cannot be affected again by the same hound archon’s aura for 24 hours.

Built for Knighthood: You do not receive a penalty to movement from wearing heavy armor. All other movement penalties still apply normally.

Canine Shapechange (Su): A hound archon can assume any canine form of Small to Large size. While in canine form, the hound archon loses its bite, slam, and greatsword attacks, but gains the bite attack of the form it chooses. For the purposes of this ability, canines include any coyote/dog/fox/jackal/wolf -like animal of the animal type. Celestial plane: At will at 1st level. All Other Planes: Once per long rest at 1st level. Then once per short rest at 5th level. Then thrice per short rest at 9th level. At will at 15th level.

Detect Alignment at 3rd level once per short rest

(what level does this activate?) Hound Archon Spell Casting 1: You can now cast Aid x3/Long Rest and Continual Flame x3/Long Rest and Tongues spell is always active unless you choose for it not to be or unless it is dispelled. If you deactivate Tongues or it is dispelled you can use an Action to reactivate it.

(what level does this activate?) Hound Archon Spell Casting 2: Requires Hound Archon Spell Casting 1. Gain the ability to cast Teleportation Circle x1/Long Rest without expending a spell slot.

(what level does this activate?) Hound Archon Spell Casting 3: Requires Hound Archon Spell Casting 1 & 2. Can now cast Teleport x1/Long Rest and can cast Magic Circle a number of times per Long Rest equal to Wisdom Modifier without expending a spell slot..

(what level does this activate?) Hound Archon Resistances 1: Gain Resistance to Lightning and Poison Damage and have advantage on saves vs Poison. Also gain +1 Constitution.

(what level does this activate?) Hound Archon Resistances 2: Requires Hound Archon Resistances 1. Gain Immunity to Lightning damage and Petrification and gain resistance to Bludgeoning, Slashing and Piercing damage from non-magical weapons unless wielded by Evil creatures.

(what level does this activate?) Hound Archon Hide: Gain Natural Armour, AC now calculated as 10+ Wis Bonus +Dex, this does not stack with AC from armor or shields its either/or as per the Monk unarmored defense ability. Your Bite attack now deals 1d6 piercing damage and your claw attacks now deal 1d4 slashing damage.

Hound's Loyalty: When an enemy is adjacent to a bloodied ally you gain a +1 racial bonus to attack rolls and a +2 racial bonus to bull rush attempts against that enemy.

I'm also toying with the idea that maybe hound archons either don't sleep (but still rest... they are on a sleepless watch) or that they don't do long rests, but require multiple short rests because dogs.... or....  they don't sleep in the celestial planes, but do in the material planes.

An important thing to remeber is that in 3.5e Hound Archons as a player race were the equivalent of a level 11 character in terms of power. Although direct comparisons with 5e are a bit hit and miss I think the best way to make it playable would be to do it as a base race in line with Teifling and then have a homebrew class to fill in the racial options.

Something like this:

https://drive.google.com/file/d/1-CtBepfU6jJ1_DenXsQXwKiqJ3F0yepx/view?usp=sharing

Ooh, I like that.  I still will need to make a few modifications to it.... but not much at all.  Thank you.

What do you think of this:

Hound Archon 

Type: Humanoid at first, then Celestial Outsider

Alignment Always starting off as some form of Good Alignment but experiencing the Prime Material Plane can/has led some Hound Archons down a darker path that leads away from their Celestial peers. If a character strays away from the good alignment, their powers are stripped until they properly atone and reconcile with their patron deity. Usually Lawful, but not necessarily.

Lifespan: Hound Archons are occasionally created/evolved from the souls of departed canine (wolf/fox/dog/coyote/jackal) that are found to be worthy by a good-aligned deity. When a hound archon is "born" it'll quickly grow to physical maturity by the age of 5. After reaching physical maturity they age very slowly on the material plane, living up to 300 years old. When a hound archon "dies" it returns to the Celestial Plane and cannot return to the Material Plane.

Immortal Origin: Your spirit is native to the Astral Sea, so you are considered an immortal creature for the purpose of effects that relate to creature origin. At time of character creation pick a Deity that resides on one of the Celestial Planes as your Hound Archons creator. When a Hound Archon is created on one of the Celestial Planes they are often sent out on a "Proving Quest". These quests involve being sent to the Prime Material Plane where the Hound Archon is to conduct themselves in ways that promote their Celestial creators view. These Hound Archons are much weaker than their compatriots and it is this Proving Quest that builds their celestial powers and traits until they become a fully-fledged Hound Archons in the eyes of their Celestial compatriots. During this Proving Quest the Hound Archon is referred to as a Hound Exemplar as they are to be seen as an example of what their Deity represents and many Hounds use "Exemplar" as a title during this time.

Names: When the Hound Archon sets out on their Proving Quest they adopt a name local to the area of the Prime Material Plane they are on. When introducing themselves they will often use the Exemplar Title, their chosen name and Celestial home plane in full such as; “Greetings, I am Exemplar Thommin of Brightwater”

Hit Dice: You only gain bonus HP at the levels shown in the table below, this is to partly offset some of the more powerful racial abilities gained.

Size: Medium. 4 ft tall to 7 foot tall, depending on "breed".

Speed: base walking speed is 40 feet

Languages: Celestial and one other language from this list: Common, Draconic, Dwarven, Elven, Gnomish, Halfling, Infernal, Sylvan.

Vision: Darkvision: You can see in dim light within 60 feet of you as if it were bright light, and in darkness as if it were dim light. You can't discern color in any lighting, only shades of grey.

Ability Scores: +2 Strength, +2 to either Constitution, Wisdom, or Charisma (depending on "breed"). (Your choice here also decides what spell casting ability modifier you use for your racial spell casting as well).

Racial Skills: A hound archon’s class skills are Athletics, Stealth, Perception, and Religion.

Favored classes (in descending order): Hound Archon (both a race and a class that cannot be taken seperately), Paladin, Cleric, Druid, Ranger, Zealot Barbarian, (Religious) Lore Bard.

Multiclassing: For multiclassing purposes, the Hound Archon racial class does not have any pre-requisite ability scores to enter it.

Suggested Backgrounds: Due to their nature Hound Archons should only have Acolyte or Soldier backgrounds from the PHB or Far Traveller from the SCAG.

Natural Weapons: Bite (1d4+str), Claws (1d4+str modifier per hand), and slam (1d4). A hound archon’s natural weapons, as well as any weapons it wields, are treated as good-aligned and lawful-aligned for the purpose of overcoming damage reduction.

Code of Conduct: Hound Archons are expected to uphold a code of conduct that represents their Deity’s ideology. This functions much like a Paladins Oath. Repeatedly failing to uphold these ideals results in the loss of all spell casting abilities until atonement has been made, this also includes spell casting gained from the racial abilities below. (At DM option other patrons may step in to grant these powers back).

Advancement: Hound Archon/Exemplars gain experience as normal adventurers do but can choose to invest that XP into normal Classes or into developing their racial abilities to become true Hound Archons. If they Choose to invest their XP into developing their racial abilities they advance as follows:

Level Proficiency Bonus Hit Dice Abilities
1 +2 d8 Canine Shapechange 1, Celestial Heritage 1, Celestial Hide, & Celestial Nature
2 +2 d8 Celestial Heritage 2
3 +2 d8 Celestial Heritage 3
4 +2 ASI, Built for Knighthood, & Celestial Heritage 4
5 +3 d8 Canine Shapechange 2, Keen Senses
6 +3 Celestial Heritage 5, Natural Intimidation
7 +3 d8 Aura of Menace
8 +3 ASI, Celestial Heritage 6
9 +4 d8 Celestial Heritage 7
10 +4 Celestial Heritage 8
11 +4 Celestial Heritage 9

Abilities explained:

Celestial Heritage 1: You gain the Light and Message cantrips and can cast them at will. You can also Canine Shapechange x1/Long Rest (LR), this functions as per the Druid ability Wildshape but the duration is max 1 hour.
If you chose to put your +1 ability score adjustment into Wis then Wis is your spellcasting modifier for these, if you put it into Cha then Cha is your spell casting ability modifier for these.

Canine Shapechange 1: A hound archon can assume any canine form of Small to Large size. While in canine form, the hound archon loses its bite, slam, and greatsword attacks, but gains the bite attack of the form it chooses. For the purposes of this ability, canines include any coyote/dog/fox/jackal/wolf -like animal of the animal type. While in canine form, a hound archon also gains a +4 circumstance bonus on Hide and Survival checks.

Celestial Hide: You have resistance to Bludgeoning, Slashing and Piercing damage unless it is from magical weapons or from a creature of evil alignment. You also have resistance to Lightning and Poison Damage and advantage on saving throws vs. Poison. You can also calculate your AC as per the Barbarian Unarmored Defense ability.

Celestial Nature: You have evolved to the first stage of your Hound Archon potential. Your creature type becomes Humanoid Celestial, this means you will now be affected by certain spells and abilities, such as but not limited to: Ranger Favoured Enemy, Banishment, Dispel Evil & Good, Magic Circle and Protection from Evil & Good. You also gain Darkvision: 60ft (as usual you cannot discern colours, only shades of grey).

Celestial Heritage 2:
You gain the following spell casting abilities: You can now also cast Aid x1/LR as a level 2 spell, Continual Flame x1/LR and Detect Evil & Good x3/LR. These spells require no material components and use the same spellcasting ability modifier as your base Celestial Heritage feature. You also gain +2 Constitution, should you lose your spellcasting ability by not upholding your Code of Conduct you also lose this Constitution bonus as well.

Celestial Heritage 3:
Your spell casting abilities change as follows: You can now also cast Aid x3/LR as a level 2 spell, Continual Flame x3/LR and Detect Evil & Good @ Will. You gain resistance to necrotic damage and radiant damage. You can also cast Invisibilty on yourself x1/LR with a duration of one hour.

Ability Score Increase (ASI):
At Level 4, As per normal character advancement you can choose either and Ability Score Increase or Feat.

Built for Knighthood: You do not receive a penalty to movement from wearing heavy armor. All other movement penalties still apply normally.

Celestial Heritage 4:
Celestial Power further empowers your physical form granting +2 Strength (max of 20), however, should you lose your spellcasting ability by not upholding your Code of Conduct you also lose this strength bonus as well.
You are now always under the effects of the Tongues spell unless you chose not to be (requiring a Bonus Action to switch it off) or unless it is dispelled. If you turn it off or if it is dispelled you can use an Action to reactivate it.

Canine Shapechange 2:
Your connection to your Celestial plane deepens and you can now Canine Shapechange at will but still each form last for upto 1 hour.

Keen Senses: You gain advantages to perception and investigation checks involving sight and/or smell and/or hearing. (certain "breeds" get higher smell checks). In addition, you can use your bonus action to roll perception and attempt and sniff out the location of an invisible or hiding creature, the DC for this is the creatures CR minus your proficiency bonus. The creature must have a scent for this feature to work.

Celestial Heritage 5:
Your Bite and Slam attacks now deal d6+str damage instead of d4+str. Natural Intimidation: You gain advantage on Intimidation checks

Aura of Menace: A righteous aura surrounds hound archons that fight or get angry. Any hostile creature within a 10-foot radius of a hound archon must succeed on a Will save (DC 16) to resist its effects. The save DC is Charisma-based, and includes a +2 racial bonus. Those who fail become frightened for 24 hours, take a –2 penalty on attacks, AC, and saves for 24 hours or until they successfully hit the hound archon that generated the aura. A creature that has resisted or broken the effect cannot be affected again by the same hound archon’s aura for 24 hours.

Ability Score Increase (ASI):
At Level 8, As per normal character advancement you can choose either and Ability Score Increase or Feat.

Celestial Heritage 6:
You physical form is so infused with celestial power that you now have advantage on saving throws vs. Magic. You gain advantage on constitution saving throws. You can now also cast Teleportation Circle x1/LR and Prayer for Healing 1xLR.

Celestial Heritage 7:
You can now cast Aid as a level 2 spell at will and Continual Flame at will. You can also cast Invisibilty on yourself at will. You also gain +2 Charisma (max 20) however, should you lose your spellcasting ability by not upholding your Code of Conduct you also lose this Charisma bonus as well.

Celestial Heritage 8:
As you near the apex of your Celestial ability you feel more empowered. You gain +2 Wisdom (max 20), however, should you lose your spellcasting ability by not upholding your Code of Conduct you also lose this Wisdom bonus as well.
You also gain Immunity to Lightning Damage and the Petrification Condition.

Celestial Heritage 9:
You are now a fully fledged Hound Archon.
You gain a further +2 Strength (Max 20), however, should you lose your spellcasting ability by not upholding your Code of Conduct you also lose this Strength bonus as well.
You are now cast Magic Circle as a level 3 spell at will.

Maybe also something like:

The higher the class level, the less need for actual sleep.  Short and long rests are still required, but actual sleeping can be replaced with dozing, meditating, stuff like that.

A few thinks come to mind, I nerfed my version as much as I could to mainatin the feel of the 3.5 e and I still think it is overpowered....

I would say to try and resist adding more bells and whistles though, if you take this character to level 20 you have room to multclass to get extra abilities. Having said that, "your cosmology, your rules" so if you are happy with it no need to read any further.

But going through it......

As a playable race Hound Archon is already more powerful than standarad races and comparable level classes, at level 11 it effectively has: a cantrip at will, a level 1 spell at will, 2x level 2 spells at will, 2x level 3 spells at will and a level 5 spell once per day (it should actually be a level 7 teleport but I nerfed it down to a level 5 telepoertation circle), not to mention natural armour, basic shapeshifting powers and a couple of resistances/immunties. Adding 3 more spells (Light, Invisibility, Pray for Healing) and giving them Resistance to Necrotic and Radiant Damage is tacking on more powers which hound archons don't appear to have in any form or incarnation I can find so it is ramping up the power level another few notches so I would leave those off.

The base race should have bite and slam attacks, no previous version had a claw attack that i can find but you could substiute slam for claw. 5e doesn't really have good and lawful aligned damage so I would just make them magical but have that as a later "class" ability otherwise you make the base race more powerful than any of the standard ones, even if it is only equivilant to magical daggers thats still something they always have so should be something they evolve into rather than just start with. Also worth noting the Player Race version in 3.5e did not get magical natural weapons.

Natural Intimidation is a bit of a mystery for me as Hound Archons are protectors of the weak and helpless in previous incarnations so not sure that fits with the aesthetic, however, going back and looking at the 3.5e monster manual and planar handbook for Hound Archon they do have a few skills available to them so you could add a skill to the base race, "choose one skill proficiency from: Athletics, Insight, Investigation, Perception, Stealth or Survival"

Aura of Menace: I did consider the version in previous editions as you have it but felt the Frightened Condition was an easier option to implement, if you keep it as you have then you might need a few adjustments: 1) The saving throw should be in line with the spell casting DC, 2) don't add a racial bonus to the DC - its hard enough as is, 3) you need a time scale for how/when a person affected by it can try to resist it again as a "fail once and you're screwed for 24 hours" is potentially quite nasty, in line with other spells/abilities it would likely be another save attempt at the end of each turn, 4) I would probably adapt the first line to read "Hound Archons can use a bonus action to emit an aura of menace when they fight or get angry" just to make it a conscious thing they can activate.

Built for Knighthood: I am not sure this fits with previous lore/incarnations. Hound Archons in previous editions didn't really wear armour as they had rediculously high natural AC, in 5e terms they would be strutting around in AC19 to 24 fairly easiliy, I nerfed it to the Barbarian Unarmoured Defence to not over power it too much. The 3.5e version of the playavble race did not grant any Armour or Shield Proficencies, it does say however they are proficient with all simple and martial weapons (which I misssed on my last coouple of read throughs) so you could give them simple and martial weapon proficencies either as part of the base class or squeezed in some where into the earlier class levels.

As for sleep, that sort of depends on your cosmology, previous versions had no special abilities to avoid having to rest or sleep. If you regard them as Angels then technically they wouldn't need to eat, drink or sleep. Personally I would leave them with the need to sleep and rest like other characters, at a push I might go for a Elf Trance or Warforged Sentries Rest style ability.

As a PS to the above....

I'm working on a conversion of the Avoral Guardinal Race form 3.5e to 5e and realised the stat bumps they factored into these player races don't make much sense.

The ability scores for the Hound Archon in the monster manual were: Str 15, Dex 10, Cons 13, Int 10, Wis 13, Cha 12...which is pretty much in line with a Standard array for generating ability scores so I would now be inclined to remove all the stat bumps from the class levels.

Cool.  I'll try a re-edit once I have more time available (really busy lately with work and home life).  I'll share it with you when I get that done.

I want you to know that I really value the input you are giving.  This is a big help.  Thanks.

I sleep now.

My last post was written in delirious sleep deprivation, so, that should explain the language used.

Some of the stuff I threw in there came from homebrew hound archons on dndbeyond.  The resistance to necrotic and radiant was lifted from Aasimir (which, really seem like they could be related).  My intent was to throw everything "and the kitchen sink" into the rough draft and then hone it down to something feasible.

The idea of not actual sleeping came from this:  https://imgur.com/gallery/mNSpe7i which also re-invigorated me to work on this.

Edit:

Maybe invisibility should be scrapped, but I do see in previous editions something about having advantages for sensing something invisible nearby.  Light and Pray for Healing were grabbed from homebrews but they made some sense due to the celestial nature.  Maybe they should go too.

I added claw attack because canines have claws and are known to use them irl to damage things (intentionally or not),  I don't understand why 5e doesn't have this for mastiff or wolf.  I suppose the damage could be adjusted to 2 piercing or slashing damage + str mod (no dice).  Otherwise, scrap it for uniformity with 5e.

Natural intimidation:  It was mentioned in a homebrew.  A wolf/jackal/coyote/bully breed/german shepherd/doberman/"scary dog" breed would make sense for this...  even maybe a breed with "little dog syndrome" like a chihuahua.  I don't see a corgi archon (imagine that) getting this.  Then there are questionable breeds like fox and labrador retriever.  Eh.  this probably should be an optional skill.

Aura of Menace:  The caster level confuses me.  I usually play nonmagical characters.  What would you place the DC at?  I think making it 24 hours maybe too long, but 1 hour is definitely too short.  3/4/7/12 hours?

The Forgotten Realms wiki seems to think that Hound Archons level up in ranks and eventually evolve into Warden Archons, which in turn level up in ranks and then evolve into Sword Archons, then Trumpet Archons, then Aasimon/Angels.  FFFFirst I've heard of that.

Quote from Post_Mortem >>

The idea of not actual sleeping came from this:  https://imgur.com/gallery/mNSpe7i which also re-invigorated me to work on this.

Re this link...as a dog owner and someone whose had to have two cats put to sleep, all i can say is...I'm not crying, I've just got something in my eyes......

My dog is a chihuahua and so little dog syndrome is very much a thing but I think its more decpetion than intimidation judging by hte amount of times my dog runs behind me when another dog barks back.

Racial DC wise its usually calculated as: 8 + one ability modifier + Proficiency bonus, so I would go for Wis or CHa for a Hound Archon, that would give it a potential range between 10 and 19 depending on level.

Hound Archons are what happens to the best bois and goodest grrls after they cross the Rainbow Bridge.... 

Trance makes more sense to me.  I'm tempted to make this a required astral projection to the Celestial Plane from whence they came for recharging....  but I can see this being abused for other purposes....  I want to change the wording more for trance, but I'm blanking on what.

I'm still struggling with Aura of Menace.

Anyways...  next draft:

Hound Archon 

Type: Humanoid at first, then Celestial Outsider

Alignment Always starting off as some form of Good Alignment but experiencing the Prime Material Plane can/has led some Hound Archons down a darker path that leads away from their Celestial peers. If a character strays away from the good alignment, their powers are stripped until they properly atone and reconcile with their patron deity. Usually Lawful, but not necessarily.

Lifespan: Hound Archons are occasionally created/evolved from the souls of departed canine (wolf/fox/dog/coyote/jackal) that are found to be worthy by a good-aligned deity. When a hound archon is "born" it'll quickly grow to physical maturity by the age of 5. After reaching physical maturity they age very slowly on the material plane, living up to 300 years old. When a hound archon "dies" it returns to the Celestial Plane and cannot return to the Material Plane. Immortal Origin: Your spirit is native to the Astral Sea, so you are considered an immortal creature for the purpose of effects that relate to creature origin. At time of character creation pick a Deity that resides on one of the Celestial Planes as your Hound Archon's creator. When a Hound Archon is created on one of the Celestial Planes they are often sent out on a "Proving Quest". These quests involve being sent to the Prime Material Plane where the Hound Archon is to conduct themselves in ways that promote their Celestial creator's view. These Hound Archons are much weaker than their compatriots and it is this Proving Quest that builds their celestial powers and traits until they become a fully-fledged Hound Archons in the eyes of their Celestial compatriots. During this Proving Quest the Hound Archon is referred to as a Hound Exemplar as they are to be seen as an example of what their Deity represents and many Hounds use "Exemplar" as a title during this time.

Names: When the Hound Archon sets out on their Proving Quest they adopt a name local to the area of the Prime Material Plane they are on. When introducing themselves they will often use the Exemplar Title, their chosen name and Celestial home plane in full such as; “Greetings, I am Exemplar Thommin of Brightwater”

Hit Dice: You only gain bonus HP at the levels shown in the table below, this is to partly offset some of the more powerful racial abilities gained.

Size: Medium. 4 ft tall to 7 foot tall, depending on "breed".

Speed: base walking speed is 40 feet

Languages: Celestial and one other language from this list: Common, Draconic, Dwarven, Elven, Gnomish, Halfling, Infernal, Sylvan.

Vision: Darkvision: You can see in dim light within 60 feet of you as if it were bright light, and in darkness as if it were dim light. You can't discern color in any lighting, only shades of grey.

Ability Scores: +2 Strength, +2 to either Constitution, Wisdom, or Charisma (depending on "breed"). (Your choice here also decides what spell casting ability modifier you use for your racial spell casting as well).

Racial Skills: A hound archon chooses 2 class skills from Athletics, Intimidation, Insight, Investigation, Perception, Religion, and Stealth.

Favored classes (in descending order): Hound Archon (both a race and a class that cannot be taken seperately), Paladin, Cleric, Druid, Ranger, Zealot Barbarian, (Religious) Lore Bard.

Multiclassing: For multiclassing purposes, the Hound Archon racial class does not have any pre-requisite ability scores to enter it.

Suggested Backgrounds: Due to their nature Hound Archons should only have Acolyte or Soldier backgrounds from the PHB or Far Traveller from the SCAG.

Natural Weapons: Bite (1d4+str), Claws (2 piercing or slashing +str modifier per hand), and slam (1d4). A hound archon’s natural weapons, as well as any weapons it wields, are treated as good-aligned and lawful-aligned for the purpose of overcoming damage reduction.

Simple and Martial Weapons Proficiency

Code of Conduct: Hound Archons are expected to uphold a code of conduct that represents their Deity’s ideology. This functions much like a Paladin's Oath. Repeatedly failing to uphold these ideals results in the loss of all spell casting abilities until atonement has been made, this also includes spell casting gained from the racial abilities below. (At DM option other patrons may step in to grant these powers back).

Trance: Hound Archons don’t need to sleep. Instead, they meditate deeply, remaining semiconscious, for 4 hours a day. (The Common word for such meditation is “trance.”) While meditating, you can dream after a fashion; such dreams are actually mental exercises that have become reflexive through years of practice. After resting in this way, you gain the same benefit that a human does from 8 hours of sleep.

Advancement: Hound Archon/Exemplars gain experience as normal adventurers do but can choose to invest that XP into normal Classes or into developing their racial abilities to become true Hound Archons. If they Choose to invest their XP into developing their racial abilities they advance as follows:

Level Proficiency Bonus Hit Dice Abilities
1 +2 d8 Canine Shapechange 1, Celestial Heritage 1, Celestial Hide, & Celestial Nature
2 +2 d8 Celestial Heritage 2
3 +2 d8 Celestial Heritage 3
4 +2 ASI & Celestial Heritage 4
5 +3 d8 Canine Shapechange 2, Keen Senses
6 +3 Celestial Heritage 5
7 +3 d8 Aura of Menace
8 +3 ASI, Celestial Heritage 6
9 +4 d8 Celestial Heritage 7
10 +4 Celestial Heritage 8
11 +4 Celestial Heritage 9

Abilities explained:

Celestial Heritage 1: You gain the Message cantrip and can cast them at will. You can also Canine Shapechange x1/Long Rest (LR), this functions as per the Druid ability Wildshape but the duration is max 1 hour.
If you chose to put your +1 ability score adjustment into Wis then Wis is your spellcasting modifier for these, if you put it into Cha then Cha is your spell casting ability modifier for these.

Canine Shapechange 1: A hound archon can assume any canine form of Small to Large size. While in canine form, the hound archon loses its bite, slam, and greatsword attacks, but gains the bite attack of the form it chooses. For the purposes of this ability, canines include any coyote/dog/fox/jackal/wolf -like animal of the animal type. While in canine form, a hound archon also gains a +4 circumstance bonus on Hide and Survival checks.

Celestial Hide: You have resistance to Bludgeoning, Slashing and Piercing damage unless it is from magical weapons or from a creature of evil alignment. You also have resistance to Lightning and Poison Damage and advantage on saving throws vs. Poison. You can also calculate your AC as per the Barbarian Unarmored Defense ability.

Celestial Nature: You have evolved to the first stage of your Hound Archon potential. Your creature type becomes Humanoid Celestial, this means you will now be affected by certain spells and abilities, such as but not limited to: Ranger Favoured Enemy, Banishment, Dispel Evil & Good, Magic Circle and Protection from Evil & Good. You also gain Darkvision: 60ft (as usual you cannot discern colours, only shades of grey).

Celestial Heritage 2: You gain the following spell casting abilities: You can now also cast Aid x1/LR as a level 2 spell, Continual Flame x1/LR and Detect Evil & Good x3/LR. These spells require no material components and use the same spellcasting ability modifier as your base Celestial Heritage feature.

Celestial Heritage 3: Your spell casting abilities change as follows: You can now also cast Aid x3/LR as a level 2 spell, Continual Flame x3/LR and Detect Evil & Good @ Will. You gain resistance to necrotic damage and radiant damage.

Ability Score Increase (ASI): At Level 4, As per normal character advancement you can choose either and Ability Score Increase or Feat.

Celestial Heritage 4: You are now always under the effects of the Tongues spell unless you chose not to be (requiring a Bonus Action to switch it off) or unless it is dispelled. If you turn it off or if it is dispelled you can use an Action to reactivate it.

Canine Shapechange 2: Your connection to your Celestial plane deepens and you can now Canine Shapechange at will but still each form last for upto 1 hour.

Keen Senses: You gain advantages to perception and investigation checks involving sight and/or smell and/or hearing. (certain "breeds" get higher smell checks). In addition, you can use your bonus action to roll perception and attempt and sniff out the location of an invisible or hiding creature, the DC for this is the creatures CR minus your proficiency bonus. The creature must have a scent for this feature to work.

Celestial Heritage 5: Your Bite and Slam attacks now deal d6+str damage instead of d4+str.

Aura of Menace: Hound Archons can use a bonus action to emit an aura of menace when they fight or get angry. Any hostile creature within a 10-foot radius of a hound archon who has raised their aura of menace must succeed on a Will save to resist its effects. The save DC is the same as the spellcasting DC. Those who fail become frightened for 7 hours, take a –2 penalty on attacks, AC, and saves for 7 hours or until they successfully hit the hound archon that generated the aura. A creature that has resisted or broken the effect cannot be affected again by the same hound archon’s aura for 7 hours.

Ability Score Increase (ASI): At Level 8, As per normal character advancement you can choose either and Ability Score Increase or Feat.

Celestial Heritage 6: You physical form is so infused with celestial power that you now have advantage on saving throws vs. Magic. You gain advantage on constitution saving throws. You can now also cast Teleportation Circle x1/LR.

Celestial Heritage 7: You can now cast Aid as a level 2 spell at will and Continual Flame at will.

Celestial Heritage 8: As you near the apex of your Celestial ability you feel more empowered. You also gain Immunity to Lightning Damage and the Petrification Condition.

Celestial Heritage 9: You are now a fully fledged Hound Archon. You are now cast Magic Circle as a level 3 spell at will.

only things i could see amending are:

Canine Shapechange 1: change  "+4 circumstance bonus on Hide and Survival checks" to a flat advamtage on the roll or a bonus d4, I can't think of any other abilities, spells or feats that grant a flat +? to a roll.

Keen Senses: Not so sure on the sniffing out invisible creatures as a bonus action, I think I'd DM it more as an opposed passive stealth of the invisible person vs the passive perception of the hound so i would likely lose it.

Aura of Meance: Will save should be Wisdom save.

There was something else I thought up about a change, but I forgot.  If I remember, I'll throw it in there and see what you think.

That opposed stealth check you mention.instead of a bonus action, maybe make it a full action with advantage?  Because I figure it is for when the hound archon is actively searching for the invisible thing.  the passive/passive check might be the start of the hunt for the invisible thing (for instance, the hound archon passively smells something and then starts trying to find what it smelled... very beagle-ish).  I think there should be some sort of mechanic for this (advantage?) but honestly, I don't know what or how to word it.

I have no memory of the other thing was that I was thinking about changing.

I would just reword it as:

"Keen Smell: If you can smell it, you can probably find it. You gain advantage on any Percpetion check involving smell and as long as their is a scent trail to follow you also gain advantage on any survival check to track a creature"