I am playing a tiefling paladin of conquest which uses a Maul and I am torn between three choices due to Tasha's. Any feedback or insights would be useful.

Infernal Constitution: Resistance to cold and poison with ADV on poison checks (Conditionally useful, but a Paladin already has jacked saves at level 6, half damage guaranteed from 2 fairly common sources does sound nice though)

Resistance CON: Add proficiency to CON checks (Saves are already boosted at level 6 and I am unsure if this would be overkill.)

Crusher: move target 5', ADV attacks after scoring a critical on target (More battlefield control and critical hit based ADV, I can't tell is this sounds more interesting than it actually is. I do use my maul multiple times every game)

I'll throw in a fourth option, and one of my favorite additions from Tasha's: Skill Expert. Grabbing +1 con and expertise in a social skill would be a really fun way to flesh out your out of combat abilities.

What level is this? Are we talking level 4 ASI? If so I think infernal constitution is really cool to have for a number of levels before your aura comes online. And even then, resistance to the three most common energy types is excellent. 

Crusher will scale with your party composition. Have some teammates adept at setting up deadly AOE's? Crusher will perform. Forced movement is generally good, but hard to quantify. I think being limited to 5 feet makes this one pretty medium unless your team supports it. The crit text means basically nothing to me. Especially on a paladin that will be pouring smite damage into crits and looking to kill the target outright.

I understand the appeal of resilient for constitution saves but I don't think it's necessary. Paladin's aren't known for their concentration spells. 

Out of your three options and my addition of skill expert I think Infernal Constitution is the strongest choice. Resistance to fire, cold and poison is quite good. 

The fact that Crusher doesn't have a save to be moved, or an opposing roll (like shieldmaster shove, for example), means that you essentially get a free disengage action when you hit. (Unless your enemy has reach)

But with that said, I'd go Infernal Constitition. It's good, and more importantly, doesn't rely on you using a specific type of weapon. What happens when you find a +2 axe/sword/etc that isn't bludgeoning damage?

My character is using a homebrew maul that grows with the character. I probably would not be using any other weapons unless in a odd predicament that dictates a different weapon. Another thing that could be cool is that those feats are usable by any bludgeoning attack including spells or ranged attacks. Unfortunately, there are no bludgeoning ranged cantrips (Blessed Warrior) or long-range bludgeoning weapons. I have been leaning toward Infernal Constitution for a while now, but I was not sure how Crusher play-tested or if it was more flashy reading than mechanical usage.

I do like expertise, but this character is already set with the social skills. I chose Deception and Persuasion, but chose not to have Intimidate for RP. He is a nice sociable character and Guidance is a real help when it comes to almost every other active skill check.

Resistance con would end up helping with concentration saves, though pallys don’t usually make many. 

A sling will do bludgeoning at range, just to put that out thete.

In the end, it will depend on the party. Are you the tank? Do you see times where moving enemies around is useful? Usually, my pally wants to stay next to the bad guys to set up the rogue for sneak attack, not push them away. And crits are going to be rare enough that it’s practically a ribbon ability to get asb on the next attack. 
Id go infernal or resistance con, largely depending on the campaign and kind of enemies you face. 

Quote from theHumanChris >>

My character is using a homebrew maul that grows with the character. I probably would not be using any other weapons unless in a odd predicament that dictates a different weapon. Another thing that could be cool is that those feats are usable by any bludgeoning attack including spells or ranged attacks. Unfortunately, there are no bludgeoning ranged cantrips (Blessed Warrior) or long-range bludgeoning weapons. I have been leaning toward Infernal Constitution for a while now, but I was not sure how Crusher play-tested or if it was more flashy reading than mechanical usage.

I do like expertise, but this character is already set with the social skills. I chose Deception and Persuasion, but chose not to have Intimidate for RP. He is a nice sociable character and Guidance is a real help when it comes to almost every other active skill check.

 Well, considering how ridiculously OP that maul is you really don't need to worry about damage output. I'd say go for Skill Expert and get a social skill.

If you think the Maul is OP, comment on how. I was looking for a balanced weapon and read through a butt-load of different variations. At this point it is a +1 adamantine maul at level 5, and will be that until level 9 when it becomes a +2 adamantine maul.

The only social skill I am lacking is Intimidate and I don't really want it. I think Infernal Constitution is going to be the winner. It will make the character resistant to Fire, Clod, and Poison with ADV on Poison saves. I guess he will be the hardest drinker in the party and able to wander around in the cold in their underwear for fun.

I don't think the mechanics of your Maul are OP. It is however, quite strong to have a guaranteed magic weapon that scales with your level. But if your DM is okaying it, then that most likely means they are affording everyone a similarly powerful boon. Power is about context. 

One more stab at playing Devil's Advocate and then I'll be done ;) I'll throw out insight as the forgotten social skill. Being good at reading people and situations is very strong for a diplomat. I don't like building "faces" without it because it doesn't make sense to me to have someone so good at manipulating people that can't read them. That and expertise makes you so much better at landing those critical persuasion checks. 

I think you will be very happy going for infernal constitution. 

My skills are Persuasion, insight, Deception, Perception, and Tool: Woodworking. The idea of getting Investigation or Athletics is appealing though. I didn't take Athletics due to not having a shield or planning to be a grappler, and Investigation is more about places than folks. I wanted to make a friendly, car salesman kind of person that was compensating for being a tiefling by being everyone's best friend. Kill them with kindness sort of attitude. Conquering the hearts and minds of the masses to control the mob. Then lead an uprising to conquer the oppressors by force. Long game strategies.

Quote from theHumanChris >>

If you think the Maul is OP, comment on how. I was looking for a balanced weapon and read through a butt-load of different variations. At this point it is a +1 adamantine maul at level 5, and will be that until level 9 when it becomes a +2 adamantine maul.

 Well, starting with it being an adamantine weapon at level 1 and going all the way up to it being able to dish out HUGE amounts of damage (at level 17 we're talking 4D6+8 bludgeoning + 12D8 radiant per hit plus 7D8 necrotic damage) and preventing the target to heal and it being able to be used as an arcane focus? Isn't that enough, you mean? Just the 3D8 automatic necrotic damage to everyone within 30 feet is super-strong.

Oh I don't think I read the Maul well enough to realize that's how it worked. Yeah, that's a lot. I'm not bothered by having an adamantine weapon with no bonus to hit or damage at 1 as nonmagical resistance is scarce at low levels and auto crits against objects is cool but not really anything to write home about. But now that I've looked at it again the way the abilities scale and stack upon each other is very, very powerful. It is incredibly friendly on your action economy as well. 

That being said I stand by my point that the Maul's balance is of no consequence if the DM is allowing it and giving everyone boons of such quality. 

You are set up well with your skills. You'll hear no more skill expert talk from me lol. Using infernal constitution to help roleplay a jovial drunk that likes to share the festivities seems perfect for your character concept.

How did you get to this amount? (at level 17 we're talking 4D6+8 bludgeoning + 12D8 radiant per hit plus 7D8 necrotic damage). If you are looking at the stacking of the final ability, it would drop a save-able, continual Chill Touch (4d8) that could persist for up to 5 rounds if max CHR. The ability would trigger as an action and then the next round the character could attack with 2 melee attacks at 2d6+3+STR. Unless you are also thinking of adding fully loaded 5th and 4th level smite on top? Assuming saves all fail and everything lands:

Rnd 1: Use Power : 4d8 necrotic

Rnd 2: 2 melee attacks smiting : 4d6+6+(STR*2) Bludgeoning + 4d8 Necrotic + 10d8 Radiant (This is hefty, but it is level 17 and just adding 4d8 Necrotic on top of what a Paladin would already be dropping didn't seem to off balance.)

Unlike weapons like Flametongue that add 2d6 to every attack as long as you want or even the boost the Holy Avenger grants, we thought this was somewhat in line with a legendary weapon at that level. It is designed for a paladin character that is worshiping Jergal, hence designing it around Chill Touch.

Quote from HeironymusZot >>

That being said I stand by my point that the Maul's balance is of no consequence if the DM is allowing it and giving everyone boons of such quality. 

 Yeah, absolutely. If everyone get OP stuff then they are no longer OP, no argument there. I've been thinking from a general perspective from what the game actually sets as a baseline.

Quote from theHumanChris>>

How did you get to this amount?

(at level 17 we're talking 4D6+8 bludgeoning + 12D8 radiant per hit plus 7D8 necrotic damage). If you are looking at the stacking of the final ability, it would drop a save-able, continual Chill Touch (4d8) that could persist for up to 5 rounds if max CHR. The ability would trigger as an action and then the next round the character could attack with 2 melee attacks at 2d6+3+STR. Unless you are also thinking of adding fully loaded 5th and 4th level smite on top? Assuming saves all fail and everything lands:

Rnd 1: Use Power : 4d8 necrotic

Rnd 2: 2 melee attacks smiting : 4d6+6+(STR*2) Bludgeoning + 4d8 Necrotic + 10d8 Radiant (This is hefty, but it is level 17 and just adding 4d8 Necrotic on top of what a Paladin would already be dropping didn't seem to off balance.)

Unlike weapons like Flametongue that add 2d6 to every attack as long as you want or even the boost the Holy Avenger grants, we thought this was somewhat in line with a legendary weapon at that level. It is designed for a paladin character that is worshiping Jergal, hence designing it around Chill Touch.

 Yeah, but a flame tongue deals fire damage which is one of the more common resistances, can't cause autocrits and don't have all of the extra damage riders and bonuses to hit. 

Ah, I see it. All I did was edit the range to 10' and made a couple verbiage changes to clarify some of the points you had made. I totally forgot about the additional d8 from improved divine smite. I also was not thinking of the damage stacking from the aura effect and the single target effect. The effect is intended to be either/or.

Quote from theHumanChris >>

Ah, I see it. All I did was edit the range to 10' and made a couple verbiage changes to clarify some of the points you had made. I totally forgot about the additional d8 from improved divine smite. I also was not thinking of the damage stacking from the aura effect and the single target effect. The effect is intended to be either/or.

 Still OP. Especially since the target can't regain HP and has disadvantage on attack rolls. Add to that that it takes a whole action and Wisdom save (why Wisdom? Con makes more sense) along with everything else and we're back to square one, it's either OP or badly written, or both.

Anyway, the point about damage output still stands. Investigation, Religion, History or Athletics are all good skills that could work for the character.

Cheers!

Since you're playing a conquest paladin, you're not really using your concentration on anything major. If anything, most of the time you'll be using your spell slots to smite. So, I don't think you want res:con. 

Crusher may be your best bet, but even then I don't think it's the winner here. Consider the following: part of crusher's benefits may be less beneficial for you. If you crit with your maul, you'll probably kill whatever it is you're targeting, cause I can't think of a single paladin who hasn't followed THE LAW of smiting on crits. If you crit, you got a dead target, and now your party doesn't get advantage. Crusher benefits more from a class with improved crit or easy access to advantage, both are things the conquest paladin lacks.

IMO, infernal constitution is meh-- unless you really want the flavor that your tiefling is more tiefling than most. What's considered common damage in one homebrew setting may be rare in another. I'd talk to your DM about what might be ahead in terms of damage before I'd consider taking it. I'd probably leave it off for way later. 

Now, if I were you'd, I'd Give consideration to feats that'd synergize With your Maul. 

Thank you. I was asking for balancing input because my GM thinks the idea is cool and figured having a cantrip level rider would not be to overwhelming. He left it up to me to balance which is why I was asking an extra set of eyes for assistance. I was making it paladin specific and increasing its strength in line with what I felt would be expected at those levels.

Building off of Chill Touch: Make a ranged spell Attack against the creature to assail it with the chill of the grave. On a hit, the target takes 1d8 necrotic damage, and it can't regain Hit Points until the start of your next turn. Until then, the hand clings to the target. If you hit an Undead target, it also has disadvantage on Attack Rolls against you until the end of your next turn.

At level 13 the cantrip would do 3d6 necrotic which is what I was using as my base. I chose WIS because out of the three main saves (WIS, DEX, and CON), it was the one that I felt represented the best defense against an attack on the spirit more than the flesh. It was strictly a judgement call, nothing more.

I think it might work better to reduce the AoE to 10' burst and remove the range option from level 17. My overall intent is to make a unique, character driven item that is not OP for the effective character levels instead of just randomly getting some generic magic weapon that is just temporary until the next one comes a long.

Quote from theHumanChris>>

Thank you. I was asking for balancing input because my GM thinks the idea is cool and figured having a cantrip level rider would not be to overwhelming. He left it up to me to balance which is why I was asking an extra set of eyes for assistance. I was making it paladin specific and increasing its strength in line with what I felt would be expected at those levels.

Building off of Chill Touch: Make a ranged spell Attack against the creature to assail it with the chill of the grave. On a hit, the target takes 1d8 necrotic damage, and it can't regain Hit Points until the start of your next turn. Until then, the hand clings to the target. If you hit an Undead target, it also has disadvantage on Attack Rolls against you until the end of your next turn.

At level 13 the cantrip would do 3d6 necrotic which is what I was using as my base. I chose WIS because out of the three main saves (WIS, DEX, and CON), it was the one that I felt represented the best defense against an attack on the spirit more than the flesh. It was strictly a judgement call, nothing more.

I think it might work better to reduce the AoE to 10' burst and remove the range option from level 17. My overall intent is to make a unique, character driven item that is not OP for the effective character levels instead of just randomly getting some generic magic weapon that is just temporary until the next one comes a long.

 Well, nothing in the description is in any way character driven so it is pretty much just a random generic magic weapon that for some reason automatically gets more and more powerful. Why? Just because. Also, you have effectively negated the purposefully designed shortcoming of the paladin (being able to attack at longer range and AoE) by giving yourself a ranged cantrip. So while this new version is slightly better, it is still not very appropriate.

Quote from Lostwhilefishing >>

Quote from theHumanChris>>

Thank you. I was asking for balancing input because my GM thinks the idea is cool and figured having a cantrip level rider would not be to overwhelming. He left it up to me to balance which is why I was asking an extra set of eyes for assistance. I was making it paladin specific and increasing its strength in line with what I felt would be expected at those levels.

The problem is that it's not really in line with anything.

Building off of Chill Touch: Make a ranged spell Attack against the creature to assail it with the chill of the grave. On a hit, the target takes 1d8 necrotic damage, and it can't regain Hit Points until the start of your next turn. Until then, the hand clings to the target. If you hit an Undead target, it also has disadvantage on Attack Rolls against you until the end of your next turn.

At level 13 the cantrip would do 3d6 necrotic which is what I was using as my base. I chose WIS because out of the three main saves (WIS, DEX, and CON), it was the one that I felt represented the best defense against an attack on the spirit more than the flesh. It was strictly a judgement call, nothing more.

Well, no. Resisting cold is a Con thing. The fact that you choose a save that many enemies are worse at is basically hedging the bets in your favour.

 Chill Touch inflicts necrotic damage, not cold damage.  And necrotic damage often goes off wisdom saves (Toll the Dead, for instance).

I would also look at Skill Expert to get Expertise. I'll probably go Resilient CON, because my paladin is very buff focused, and having a ridiculous CON save is really handy.