That depends on a few things. What are your stats, what level will you be playing to and party composition come to mind. Though I will say that Paladin 3/Rogue X would do fine. Go Vengeance for the channel divinity to give you advantage on your attacks for one minute, granting you sneak attack if you hit.
I've tried to make this build before, but it doesn't really work all too well.
The first problem that comes up is the stats: Paladin requires 13 STR or higher in order to multiclass in or out of it, so you have to make that a 13 just for that, on what is otherwise a DEX-based build, which is bothersome. You're (presumeably) a DEX-based build, so you need to max out DEX. You're a front-liner, so you need as much CON as you can get (14 at least, 16 if you can get it). You're a scout so WIS (for Perception) is a decently important ability (you probably want 12 or more, but 10 CAN work). Paladin also requires 13 CHA or higher, and you use it as a spellcasting ability, so you probably want a 14. You are so stat-hungry, MAD (multiple-attribute dependent) is an understatement. This problem is pretty much unsolvable, unless you roll for stats, and roll incredibly well. It's certainly not possible with Array, and probably impossible with Point-Buy as well.
Secondly, it just doesn't really work very well. The Assassin is pretty much the worst Rogue subclass (by far, actually), and its abilities don't really work, unless your entire party is made up of Assassins. Here's why:
The 3rd-level ability, Assassinate, seems pretty good, but it's really, really, not. It ONLY does ANYTHING on the first round of combat, and ONLY if you win Initiative, AND they weren't already engaged in combat with something else. If you don't surprise someone, then you only get advantage on attacks if you roll higher initiative than them. It seems like if you surprise someone (which happens VERY rarely in Dnd; you're walking around with an entire party accompanying you, and they tend to make a lot of noise), then it would be good, but even then, it still doesn't always work. Due to how the Surprise mechanic works in 5e, a surprised creature still rolls Initiative at the same time as everyone else, and it is surprised until the end of its first turn. So, EVEN IF you surprise someone, you STILL have to win Initiative in order to get advantage (since even though surprise just makes them unable to act on their first turn, their first turn still happens), and if you lose Initiative, they won't even be surprised anymore when you attack them, so you don't even get the auto-critical effect. TL;DR: this does exactly nothing if you lose Initiative, and is pretty pitiful even if you win Initiative unless you also surprise them (which rarely happens, and almost never happens against "boss-monsters"/"BBEGs"). Incredibly situational, and relies on your initiative.
The 9th-level ability, Infiltration Expertise, is even more useless than the worst of the Ranger abilities; this is Countercharm-tier in its uselessness, except even worse. It has a SEVEN DAY charge-up (excuse me? Who, in the middle of a campaign, can take SEVEN DAYS to charge up a non-combat-oriented ability? Ridiculous), a 25gp cost per use, and an effect that doesn't even do anything tangible. Also, since you can only make personae for yourself, this is pretty much useless if you're playing in a party, which you almost certainly are. I wouldn't even bother writing this on my character sheet.
The 13th-level ability is nearly as useless as the previous; the main use is to do really good impressions of people as a joke around the campfire. Since you still look like yourself, you're probably not going to be able to assume someone else's identity by copying their speech (which you need to listen to carefully for THREE HOURS to copy), their behavior (which, again you need to observe to THREE HOURS). The only part that may be useful is the handwriting part, which seems like it would make you marginally better at forging documents in theory, but actually, you would need to make a Forgery Kit check, which this subclass DOESN'T GIVE YOU. 0/10, wouldn't even write this on my character sheet.
The 17th-level ability, Death Strike, is even more situational than Assassinate. Once again, you have to win Initiative in order to get any benefit, but this one doesn't give you any benefit at all unless you win Initiative AND surprise them, AND hit them with your 1 and only attack. Extremely cool the one time you manage to pull it off in the entire campaign, but it will pretty much never come up. Your whole deal this entire subclass is that you've been specialized for one, very situational, ability (Assassinate), and now you get an ability that doesn't do anything unless you get that situation.
TL;DR: unless you surprise your opponent AND win Initiative, exactly none of the Assassin abilities will do anything at all in combat, except for getting advantage on your first attack if you win Initiative. The Assassin subclass is absolute garbage. On an NPC, the DM can make its infiltration and surprise-oriented abilities work, but on a PC, it's really not very good.
If you roll for stats and somehow roll really well, and want to play a Rogue/Paladin multiclass, you probably don't want to pick Assassin. Arcane Trickster is pretty nice; you get access to a completely different spell list than the Paladin gives you, and you can use the Multiclass spellcasting rules to get more slots to Smite with. The Swashbuckler also works decently, and lets you take further advantage of the CHA that you have for the Paladin class.
AND HERE IS WHERE I GET TO THE PART WHERE I ACTUALLY ANSWER YOUR QUESTION AND GIVE SUGGESTIONS
If you are absolutely determined to play an Assassin Paladin, you probably won't be a particularly effective build for the effort that you have to put into it, but here we go. If I try hard enough, maybe I can get something that can be a functioning build(?).
To answer your question:
Feats you want: 1) increase DEX to 20. Used for attack rolls, damage rolls, Initiative rolls (which you need to be winning to make this build work at all), and AC all depend on this. 2) ALERT. You need to win Initiative to make Assassinate do anything, and a +5 bonus is incredible. Pick V. Human so that you pick this up at 1st-level without harming your DEX ability progression. 3) Lucky is a great Feat, and can help if you roll poorly on Initiative, your attack rolls that would get Assassinate on them, and important Saving Throws.
Level split: Rogue (Assassin) 3/Paladin (Oath of Vengeance) X. Take the three levels of Assassin first, switch to Paladin, go Oath of Vengeance, and never take Assassin again. Getting more/better spell slots for Smiting.
Paladin Subclass: as I said above, Oath of Vengeance for sure. Their Channel Divinity works very well for Rogues.
Here's a suggested build, made by me as I write this (DISCLAIMER: You could almost definitely do at least as well, if not better, by just going straight Paladin) (from here on, just think of the first huge chunk [where I talked about Assassin being a bad subclass] as the reason why I'm only taking 3 levels of Rogue):
Class: Paladin (Rogue 3/Paladin 1). Hit Points: d10. Proficiencies: [Medium Armor, Shields, Martial Weapons]. Divine Sense, Lay on Hands.
Equipment: Pick up a Shield here. We now use Rapier & Shield, and wear Studded Leather. We will now have 17 AC, as opposed to 15 without the Shield, or 14 (with original equipment), assuming no magic items.
L5: Paladin (Rogue 3/Paladin 2). Fighting Style: Dueling or Defense, Spellcasting (I can't be bothered, you can change it out every day, and we'll be using the slots for Smites anyway. Without Ritual Casting, don't worry about Rituals. I'd recommend Bless and Shield of Faith, but it doesn't really matter), Divine Smite.
L8: Paladin (Rogue 3/Paladin 5). Extra Attack (very nice; this gives us a second chance if we miss our first attack), 2nd-level Spells (pick whatever you want. Smite with the slots).
L9: Paladin (Rogue 3/Paladin 6). Aura of Protection (amazing ability is amazing).
L10+: If you get this high, you can deal with it yourself. Go straight Paladin from here. Max out DEX, then take Lucky or Inspiring Leader (if no one already has it; you only need on Inspiring Leader per party). Nothing else gives you choices except spells, and I'm not bothering with those selections anyway. At L20, we'll get 5th-level spells (the max for a Paladin), which is cool.
THIS LAST BIT IS PROBABLY THE MOST IMPORTANT PARAGRAPH SO BE SURE TO READ IT
Personally, I think that this is the best you can do if you are dead-set on playing an Assassin Paladin. I think that based on your concept (a dark warrior in service to the God of Death), a Hexadin (Paladin/Hexblade Warlock) or Soradin (Paladin/Sorcerer) would also fit your concept, and be both more effective, and more interesting to play. To get advice for those, look up guides on YouTube. Treantmonk's Temple (my favorite source of guides and builds) has an excellent Soradin Guide (https://www.youtube.com/watch?v=YSFevTby6gM) which I would *highly* recommend checking out. Nerdarchy and DawnForgedCast have Hexadin builds that come up if you search "Hexadin" on YouTube. Here's the character sheet for a Hexadin which I am currently playing: ddb.ac/characters/30378961/wL6VEi. If "Dark Warrior in Service to Kelemvor" is a misidentification of your concept, and you want to be a Rogue specifically, going straight Rogue (Arcane Trickster) with the Acolyte background, taking Magic Initiate (Cleric) and/or Ritual Caster (Cleric) should suit this concept.
One thing about making builds in DnD is that once you have a concept, even if one class/combination of classes seems to fit your build, there are sometimes other class combinations that work equally well, but are less obvious. Being able to identify characteristics of what type of character you want to play, before choosing the race/class(es) is important (IMO, at least). When you come up with a character concept, think "I want to play a character who ______." For example, "Human Rogue/Paladin" is not a character concept; "Dark warrior in service to Kelemvor" is a concept. If you take a class and then try to come up with a concept, your concept will have all types of limitations put on it before you even make it. If you take a concept first, then choose a race, class, and abilities that fulfill that concept, you will feel like you have less limitations put on yourself when you try to figure out their personality. (SIDE NOTE: Incidentally, I think alignment is the same way. If you think "I am Lawful Good, and must therefore _____," then you are just putting limitations on what your character can do. If you think "my character ________, and is therefore Lawful Good," then you won't feel like you are constrained by it).
If you ask me, most concepts involve a character being strong in battle, which is why, when I tend to make characters, I try to make them as strong as I can. Adventurers, first and foremost, are combatants. They fight, they get stronger, and then fight some more, rinse and repeat. Therefore, my vision of a "cool character" is someone who is skilled/useful in combat. For me, finely tuning a character is just as fun as playing them, if not more so.
Hope this helps! Tried to answer your question as best as I could, while also providing a couple of alternatives that also suit what I could glean of your character concept. I focused primarily on Assassin/Paladin like you requested, but gave my input as to why you might want to try something else, or at least consider it. For the record, just because something (namely the Assassin subclass) isn't very good, doesn't mean you can't have fun with it. Hopefully the stuff at the end that I said about character concepts at least piques your interest; I think that it's the most fun way to make a character, and can remove some limitations that you may be unintentionally imposing on yourself. I hope that whatever you do with this character, they are someone who you can enjoy playing, and that you have fun while doing so! Always remember, when playing DnD, the number 1 goal is to have fun! :)
(PS, was this response comprehensive enough lol? I totally got absorbed in it and lost track of how much I had written haha) :)
One thing to keep in mind is that you don't have to be an Assassin to be an assassin and you don't need to be a paladin to be the champion of a god.
When you're having trouble fitting a character concept to a build, you need to step back and ask yourself how you want the character to work in and out of combat. Nail down what you want mechanically, then pick the build that can do that, then reflavor it. An god's assassin could be a warlock or a cleric or a rogue or a monk or just about anything. You just need to describe it and play it as such.
One thing to keep in mind is that you don't have to be an Assassin to be an assassin and you don't need to be a paladin to be the champion of a god.
When you're having trouble fitting a character concept to a build, you need to step back and ask yourself how you want the character to work in and out of combat. Nail down what you want mechanically, then pick the build that can do that, then reflavor it. An god's assassin could be a warlock or a cleric or a rogue or a monk or just about anything. You just need to describe it and play it as such.
So, basically, what Blue said.
This is a very good summary of the point I tried to make at the end. Couldn't agree more.
I see. Well ty for the advice so far, I am open to trying other rogue subclasses, but wanna stay rogue paladin. I'm loving the vengeance paladin idea. What subclasses of rogue would work better and what decisions would you makes based on that. Also would it be better to throw in sorc maybe? For better spellcasting and higher slots to feed into smite?
I have actually played this. but not like you would think. the end split was pal 6/assassin 3/ battle master 3/ sorcerer 8. the first round nova was insanely high. it was really bad after the first round but it was so much fun to play. he would quicken a hold person and proceed to smite the opponents brains out.
it was something like 42d8(weapon and smites, doubled from assassinate and doubled again from hold person) + 8d6(sneak attack) + 4d8(superiority dice) + 10.
it averaged out for around 218 damage. not the highest, but hilarious to role-play...........and out of the shadows comes bill, in a blaze of radiant glory. you find yourself unable to move as he strikes you down
this was a lvl 20 1 shot tho I dont recommend in an actually game
I'd still recommend the build that I outlined in my post from before; start with Rogue 3 and go straight Paladin from there. Vengeance is your best bet for sure. I don't really see a point in going Sorc if you're already taking Rogue AND Paladin. While it will give you access to Metamagic and increase your spell slot progression, you've already greatly delayed it by taking Rogue 3, and if you end up taking more than 3 levels of Rogue you will have delayed it even further. Multiclassing can make a strong build, but if you take from too many different classes it just becomes bloated and awkward, since you just end up with a menagerie of low-leveled abilities that don't necessarily have any synergy with each other. If you take more than 3 levels of Rogue, you probably shouldn't be looking for a third class. As amgonnayeet said, his build was for a lv 20 one-shot, so it was good at lv20, but most of your campaign won't take place at lv 20, and he even said he wouldn't recommend it. Frankly, if we're taking Rogue at all, I wouldn't recommend multiclassing further. Think of it this way: the Soradin is a build that specializes in Divine Smite, but if we're taking levels of Rogue, we've already fallen behind on that front. Better to focus on what we aren't already behind on.
For your Rogue subclass, I'd recommend either Swashbuckler (more reliable Sneak Attacks, a nice bonus to Initiative), Arcane Trickster (increase your spell slot progression by the equivalent of 2 Paladin levels, pick up some nice cantrips [you want Minor Illusion, and Booming Blade will be nice until you get Extra Attack], and you will be able to get your choice of Shield and Find Familiar [not both though, due to spell school restrictions]), or Assassin (about to explain why next paragraph). NOTE: if you take Arcane Trickster, don't worry about your INT stat. It's not a multiclass requirement, and you should pick spells that don't rely on it (no attack roll, save, etc.), like Shield, Disguise Self, etc.
Despite what I said earlier about Assassin not being very good, if you're only taking 3 levels of it, that doesn't matter as much. It's mainly bad due to having borderline unusable abilities at levels 9 and 13, an the other abilities being very situational. However, if we only take 3 levels, that won't matter at all. The 3rd-level ability, despite being very situational, is actually really good if you can get it to go off, which you can sometimes do through strategic roleplay outside of combat (don't expect to be able to use it in a dungeon-crawl though).
Frankly, no matter which Rogue subclass you take (if any), I wouldn't go more than 2 or 3 levels. Paladin is a really strong class, considered to be the best martial class by a lot of people. The more Paladin you do, the better.
The build that I showed in my first reply, where I took Variant Human with Alert, took Assassin Rogue 3, then went straight Vengeance Paladin from there should actually be a moderately good build (I think that it should be better than most builds that are aren't optimized). Taking a Rapier should be your best bet, and start using a Shield when you become proficient when you take Paladin 1. Stick with Light Armor the whole way. It's probably on the weaker side if your party is full of optimizers, or the stronger side if no one else optimizes.
I'd still recommend the build that I outlined in my post from before; start with Rogue 3 and go straight Paladin from there. Vengeance is your best bet for sure. I don't really see a point in going Sorc if you're already taking Rogue AND Paladin. While it will give you access to Metamagic and increase your spell slot progression, you've already greatly delayed it by taking Rogue 3, and if you end up taking more than 3 levels of Rogue you will have delayed it even further. Multiclassing can make a strong build, but if you take from too many different classes it just becomes bloated and awkward, since you just end up with a menagerie of low-leveled abilities that don't necessarily have any synergy with each other. If you take more than 3 levels of Rogue, you probably shouldn't be looking for a third class. As amgonnayeet said, his build was for a lv 20 one-shot, so it was good at lv20, but most of your campaign won't take place at lv 20, and he even said he wouldn't recommend it. Frankly, if we're taking Rogue at all, I wouldn't recommend multiclassing further. Think of it this way: the Soradin is a build that specializes in Divine Smite, but if we're taking levels of Rogue, we've already fallen behind on that front. Better to focus on what we aren't already behind on.
For your Rogue subclass, I'd recommend either Swashbuckler (more reliable Sneak Attacks, a nice bonus to Initiative), Arcane Trickster (increase your spell slot progression by the equivalent of 2 Paladin levels, pick up some nice cantrips [you want Minor Illusion, and Booming Blade will be nice until you get Extra Attack], and you will be able to get your choice of Shield and Find Familiar [not both though, due to spell school restrictions]), or Assassin (about to explain why next paragraph). NOTE: if you take Arcane Trickster, don't worry about your INT stat. It's not a multiclass requirement, and you should pick spells that don't rely on it (no attack roll, save, etc.), like Shield, Disguise Self, etc.
Despite what I said earlier about Assassin not being very good, if you're only taking 3 levels of it, that doesn't matter as much. It's mainly bad due to having borderline unusable abilities at levels 9 and 13, an the other abilities being very situational. However, if we only take 3 levels, that won't matter at all. The 3rd-level ability, despite being very situational, is actually really good if you can get it to go off, which you can sometimes do through strategic roleplay outside of combat (don't expect to be able to use it in a dungeon-crawl though).
Frankly, no matter which Rogue subclass you take (if any), I wouldn't go more than 2 or 3 levels. Paladin is a really strong class, considered to be the best martial class by a lot of people. The more Paladin you do, the better.
The build that I showed in my first reply, where I took Variant Human with Alert, took Assassin Rogue 3, then went straight Vengeance Paladin from there should actually be a moderately good build (I think that it should be better than most builds that are aren't optimized). Taking a Rapier should be your best bet, and start using a Shield when you become proficient when you take Paladin 1. Stick with Light Armor the whole way. It's probably on the weaker side if your party is full of optimizers, or the stronger side if no one else optimizes.
Since for some reason I can't edit this reply (not sure why not), I'll just put my would-be edit in a new reply.
Basically, what I'm trying to say is that the part that makes the Assassin Rogue/Paladin multiclass somewhat dubious is that the Rogue part and Paladin part don't fit together that well, not that Assassin isn't great. The Assassin isn't a great subclass, but it offers more synergy with Paladin than any other subclass.
In other words, if you really want to multiclass Rogue/Paladin, Assassin should be fine. If anything, the main difference between the subclasses (in this multiclass) is that Assassin will be more flavorful than the others. Assassinate has a good amount of Synergy with Paladin. Swashbuckler has a tiny bit of Synergy (literally just the fact that it uses CHA). Arcane Trickster has even less. If you want to play a Rogue/Paladin, feel absolutely free to take Assassin. You will, however, have abilities that feel like you just delayed the Paladin ones by 3 levels in exchange for some stuff you'll rarely use in combat.
In fact, your character concept doesn't even need to be a Paladin. You can be a straight-class Rogue working for a divine master without feeling the need to take Paladin and/or Cleric at all. Especially since you're serving a non-good god, perhaps the flavor of an Arcane Trickster would be even better for your concept without any multiclassing at all. Remember, to serve a god, you don't have to be a Paladin (or a Cleric) at all! People assume that a Paladin is a "champion of a god" (because that's what they were in previous editions), but if you read the flavor text in the 5e PHB, it just says that they *can* be in service to a god. They're actually supposed to be in service to an "ideal," which is chosen by their subclass.
I'm just trying to say that you don't HAVE to be a Paladin to fulfill your concept. You don't have to be a Rogue to fulfill your concept. If I were to play as a Rogue/Paladin, I'd take 3 levels of Assassin as my Rogue subclass, and then have fun roleplaying as a divinely-inspired assassin, who specializes in taking people by surprise. It seems like a fun gimmick to have, and if your DM will let you pull off the Assassinate ability every once in a while, that would be really fun to do. Just don't get overly attached to the idea of a certain class or class(es). You don't need to be a Rogue to be sneaky and assassinate people. You don't need to be a Paladin to fight for a god. If you wanted, you could fulfill your concept by taking 2 levels of Rogue and then going Trickery Cleric, with Kelemvor as your god. You could be any type of Rogue with a couple levels of Fighter and maybe the Acolyte Background or Magic Initiate (Cleric) feat. You could play a straight Rogue with the Acolyte background. I've actually played a Rogue who was a ninja specializing in gathering intelligence on behalf of the Pope of Pelor, and I was just a standard Human Arcane Trickster, with no multiclass.
What I'm trying to say is, essentially, try to be flexible. Feel free to take Assassin. Don't feel like you can't take Assassin. Don't feel like you have to take Assassin. Don't feel like you have to take Rogue. Don't feel like you have to take Paladin. Feel free to take whatever you want. In the end, you just have to roleplay as the character you're visualizing in your concept, and create a build with abilities that let you do what you imagine him doing.
Building one of these myself so thought I'd leave this here for other lurkers.
Does about 309 damage with action surge and GWM bonus attack. Or ~150 damage without them. Also has all the utility of paladin and bard spells.
Requirements: 13 Str, 13 Dex, 13 Cha
Stats: Standard Array: Dex 15, Con 12, Str 13, Cha 14, Wis 10, Int 8. If you're using Tasha's rules add +1 to Dex and +2 to Cha. (Low con won't be the worst as Shadar-Kai get resistance to everything after teleporting).
Race: Shadar-Kai (teleport guarantees surprise, meditate and trance recovers spell slots in a short rest)
Feat: GWM. You're not taking it for the +10 bonus damage per hit, you're taking it for the bonus attack you can get when you crit
Basic premise is you use a Rapier to proc sneak attack/assassinate. It's a melee weapon so can still use with GWM to get the extra attack but you won't get the +10. This also means you don't have to take the GWM penalty on attack rolls.
You take care blind fighting / defence / duelling fighting styles, but defence seems the better option.
Can proc surprise in heavy armour if you teleport but it'll use your bonus action, or use a breastplate and stealth before battle to use your bonus action to attack.
You also have an extra attack through your bard sub class and get a lot more spells as a bard for smites. You get guaranteed surprise with teleport and if you can avoid using it to get surprise you'll get a bonus attack. All your long rest things like spells and teleports recover on short rest with Shadar Kai trance so you'll never run out.
The character is an assassin for Kelemvor. What feats and level split should I take? Also what paladin subclass?
That depends on a few things. What are your stats, what level will you be playing to and party composition come to mind. Though I will say that Paladin 3/Rogue X would do fine. Go Vengeance for the channel divinity to give you advantage on your attacks for one minute, granting you sneak attack if you hit.
I've tried to make this build before, but it doesn't really work all too well.
The first problem that comes up is the stats: Paladin requires 13 STR or higher in order to multiclass in or out of it, so you have to make that a 13 just for that, on what is otherwise a DEX-based build, which is bothersome. You're (presumeably) a DEX-based build, so you need to max out DEX. You're a front-liner, so you need as much CON as you can get (14 at least, 16 if you can get it). You're a scout so WIS (for Perception) is a decently important ability (you probably want 12 or more, but 10 CAN work). Paladin also requires 13 CHA or higher, and you use it as a spellcasting ability, so you probably want a 14. You are so stat-hungry, MAD (multiple-attribute dependent) is an understatement. This problem is pretty much unsolvable, unless you roll for stats, and roll incredibly well. It's certainly not possible with Array, and probably impossible with Point-Buy as well.
Secondly, it just doesn't really work very well. The Assassin is pretty much the worst Rogue subclass (by far, actually), and its abilities don't really work, unless your entire party is made up of Assassins. Here's why:
TL;DR: unless you surprise your opponent AND win Initiative, exactly none of the Assassin abilities will do anything at all in combat, except for getting advantage on your first attack if you win Initiative. The Assassin subclass is absolute garbage. On an NPC, the DM can make its infiltration and surprise-oriented abilities work, but on a PC, it's really not very good.
If you roll for stats and somehow roll really well, and want to play a Rogue/Paladin multiclass, you probably don't want to pick Assassin. Arcane Trickster is pretty nice; you get access to a completely different spell list than the Paladin gives you, and you can use the Multiclass spellcasting rules to get more slots to Smite with. The Swashbuckler also works decently, and lets you take further advantage of the CHA that you have for the Paladin class.
AND HERE IS WHERE I GET TO THE PART WHERE I ACTUALLY ANSWER YOUR QUESTION AND GIVE SUGGESTIONS
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If you are absolutely determined to play an Assassin Paladin, you probably won't be a particularly effective build for the effort that you have to put into it, but here we go. If I try hard enough, maybe I can get something that can be a functioning build(?).
To answer your question:
Feats you want: 1) increase DEX to 20. Used for attack rolls, damage rolls, Initiative rolls (which you need to be winning to make this build work at all), and AC all depend on this. 2) ALERT. You need to win Initiative to make Assassinate do anything, and a +5 bonus is incredible. Pick V. Human so that you pick this up at 1st-level without harming your DEX ability progression. 3) Lucky is a great Feat, and can help if you roll poorly on Initiative, your attack rolls that would get Assassinate on them, and important Saving Throws.
Level split: Rogue (Assassin) 3/Paladin (Oath of Vengeance) X. Take the three levels of Assassin first, switch to Paladin, go Oath of Vengeance, and never take Assassin again. Getting more/better spell slots for Smiting.
Paladin Subclass: as I said above, Oath of Vengeance for sure. Their Channel Divinity works very well for Rogues.
Here's a suggested build, made by me as I write this (DISCLAIMER: You could almost definitely do at least as well, if not better, by just going straight Paladin) (from here on, just think of the first huge chunk [where I talked about Assassin being a bad subclass] as the reason why I'm only taking 3 levels of Rogue):
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Build Summary by level (just showing selections):
L1:
Race: Variant Human. +1 DEX, +1 CHA, Alert, Perception.
Stats (Point-Buy): STR=13, DEX=15+1=16, CON=14, INT=9, WIS=8, CHA=13+1=14.
Background: Criminal/Spy, Deception, Stealth, Dice Set, Forgery Kit.
Class: Rogue (Rogue 1). Hit Points: d8. Proficiencies: [Acrobatics, Intimidation, Investigation, Sleight of Hand], Expertise: [Perception, Stealth], Sneak Attack (1d6), Thieves' Cant.
Equipment: Rapier, Shortbow & Arrows, Burglar Pack (and the other stuff you don't get to choose, but I don't wanna write out).
L2:
Class: Rogue (Rogue 2). Cunning Action.
L3:
Class: Rogue (Rogue 3). Assassin, Bonus Proficiencies (Poisoner's Kit, Disguise Kit), Assassinate, Sneak Attack (2d6).
L4:
Class: Paladin (Rogue 3/Paladin 1). Hit Points: d10. Proficiencies: [Medium Armor, Shields, Martial Weapons]. Divine Sense, Lay on Hands.
Equipment: Pick up a Shield here. We now use Rapier & Shield, and wear Studded Leather. We will now have 17 AC, as opposed to 15 without the Shield, or 14 (with original equipment), assuming no magic items.
L5: Paladin (Rogue 3/Paladin 2). Fighting Style: Dueling or Defense, Spellcasting (I can't be bothered, you can change it out every day, and we'll be using the slots for Smites anyway. Without Ritual Casting, don't worry about Rituals. I'd recommend Bless and Shield of Faith, but it doesn't really matter), Divine Smite.
L6: Paladin (Rogue 3/Paladin 3). Sacred Oath: Oath of Vengeance, Channel Divinity, Oath Spells.
L7: Paladin (Rogue 3/Paladin 4). ASI: +2 DEX.
L8: Paladin (Rogue 3/Paladin 5). Extra Attack (very nice; this gives us a second chance if we miss our first attack), 2nd-level Spells (pick whatever you want. Smite with the slots).
L9: Paladin (Rogue 3/Paladin 6). Aura of Protection (amazing ability is amazing).
L10+: If you get this high, you can deal with it yourself. Go straight Paladin from here. Max out DEX, then take Lucky or Inspiring Leader (if no one already has it; you only need on Inspiring Leader per party). Nothing else gives you choices except spells, and I'm not bothering with those selections anyway. At L20, we'll get 5th-level spells (the max for a Paladin), which is cool.
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THIS LAST BIT IS PROBABLY THE MOST IMPORTANT PARAGRAPH SO BE SURE TO READ IT
Personally, I think that this is the best you can do if you are dead-set on playing an Assassin Paladin. I think that based on your concept (a dark warrior in service to the God of Death), a Hexadin (Paladin/Hexblade Warlock) or Soradin (Paladin/Sorcerer) would also fit your concept, and be both more effective, and more interesting to play. To get advice for those, look up guides on YouTube. Treantmonk's Temple (my favorite source of guides and builds) has an excellent Soradin Guide (https://www.youtube.com/watch?v=YSFevTby6gM) which I would *highly* recommend checking out. Nerdarchy and DawnForgedCast have Hexadin builds that come up if you search "Hexadin" on YouTube. Here's the character sheet for a Hexadin which I am currently playing: ddb.ac/characters/30378961/wL6VEi. If "Dark Warrior in Service to Kelemvor" is a misidentification of your concept, and you want to be a Rogue specifically, going straight Rogue (Arcane Trickster) with the Acolyte background, taking Magic Initiate (Cleric) and/or Ritual Caster (Cleric) should suit this concept.
One thing about making builds in DnD is that once you have a concept, even if one class/combination of classes seems to fit your build, there are sometimes other class combinations that work equally well, but are less obvious. Being able to identify characteristics of what type of character you want to play, before choosing the race/class(es) is important (IMO, at least). When you come up with a character concept, think "I want to play a character who ______." For example, "Human Rogue/Paladin" is not a character concept; "Dark warrior in service to Kelemvor" is a concept. If you take a class and then try to come up with a concept, your concept will have all types of limitations put on it before you even make it. If you take a concept first, then choose a race, class, and abilities that fulfill that concept, you will feel like you have less limitations put on yourself when you try to figure out their personality.
(SIDE NOTE: Incidentally, I think alignment is the same way. If you think "I am Lawful Good, and must therefore _____," then you are just putting limitations on what your character can do. If you think "my character ________, and is therefore Lawful Good," then you won't feel like you are constrained by it).
If you ask me, most concepts involve a character being strong in battle, which is why, when I tend to make characters, I try to make them as strong as I can. Adventurers, first and foremost, are combatants. They fight, they get stronger, and then fight some more, rinse and repeat. Therefore, my vision of a "cool character" is someone who is skilled/useful in combat. For me, finely tuning a character is just as fun as playing them, if not more so.
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END OF LONG POST
Hope this helps! Tried to answer your question as best as I could, while also providing a couple of alternatives that also suit what I could glean of your character concept. I focused primarily on Assassin/Paladin like you requested, but gave my input as to why you might want to try something else, or at least consider it. For the record, just because something (namely the Assassin subclass) isn't very good, doesn't mean you can't have fun with it. Hopefully the stuff at the end that I said about character concepts at least piques your interest; I think that it's the most fun way to make a character, and can remove some limitations that you may be unintentionally imposing on yourself. I hope that whatever you do with this character, they are someone who you can enjoy playing, and that you have fun while doing so! Always remember, when playing DnD, the number 1 goal is to have fun! :)
(PS, was this response comprehensive enough lol? I totally got absorbed in it and lost track of how much I had written haha) :)
One thing to keep in mind is that you don't have to be an Assassin to be an assassin and you don't need to be a paladin to be the champion of a god.
When you're having trouble fitting a character concept to a build, you need to step back and ask yourself how you want the character to work in and out of combat. Nail down what you want mechanically, then pick the build that can do that, then reflavor it. An god's assassin could be a warlock or a cleric or a rogue or a monk or just about anything. You just need to describe it and play it as such.
So, basically, what Blue said.
My homebrew subclasses (full list here)
(Artificer) Swordmage | Glasswright | (Barbarian) Path of the Savage Embrace
(Bard) College of Dance | (Fighter) Warlord | Cannoneer
(Monk) Way of the Elements | (Ranger) Blade Dancer
(Rogue) DaggerMaster | Inquisitor | (Sorcerer) Riftwalker | Spellfist
(Warlock) The Swarm
This is a very good summary of the point I tried to make at the end. Couldn't agree more.
I see. Well ty for the advice so far, I am open to trying other rogue subclasses, but wanna stay rogue paladin. I'm loving the vengeance paladin idea. What subclasses of rogue would work better and what decisions would you makes based on that. Also would it be better to throw in sorc maybe? For better spellcasting and higher slots to feed into smite?
I have actually played this. but not like you would think. the end split was pal 6/assassin 3/ battle master 3/ sorcerer 8. the first round nova was insanely high. it was really bad after the first round but it was so much fun to play. he would quicken a hold person and proceed to smite the opponents brains out.
it was something like 42d8(weapon and smites, doubled from assassinate and doubled again from hold person) + 8d6(sneak attack) + 4d8(superiority dice) + 10.
it averaged out for around 218 damage. not the highest, but hilarious to role-play...........and out of the shadows comes bill, in a blaze of radiant glory. you find yourself unable to move as he strikes you down
this was a lvl 20 1 shot tho I dont recommend in an actually game
“I will take responsibility for what I have done. [...] If must fall, I will rise each time a better man.” ― Brandon Sanderson, Oathbringer.
I would say Arcane Trickster, but INT is like the only stat you can afford to dump. Might still work if you just take utility spells.
If you can use UA content, the Phantom would fit your theme.
My homebrew subclasses (full list here)
(Artificer) Swordmage | Glasswright | (Barbarian) Path of the Savage Embrace
(Bard) College of Dance | (Fighter) Warlord | Cannoneer
(Monk) Way of the Elements | (Ranger) Blade Dancer
(Rogue) DaggerMaster | Inquisitor | (Sorcerer) Riftwalker | Spellfist
(Warlock) The Swarm
I'd still recommend the build that I outlined in my post from before; start with Rogue 3 and go straight Paladin from there. Vengeance is your best bet for sure. I don't really see a point in going Sorc if you're already taking Rogue AND Paladin. While it will give you access to Metamagic and increase your spell slot progression, you've already greatly delayed it by taking Rogue 3, and if you end up taking more than 3 levels of Rogue you will have delayed it even further. Multiclassing can make a strong build, but if you take from too many different classes it just becomes bloated and awkward, since you just end up with a menagerie of low-leveled abilities that don't necessarily have any synergy with each other. If you take more than 3 levels of Rogue, you probably shouldn't be looking for a third class. As amgonnayeet said, his build was for a lv 20 one-shot, so it was good at lv20, but most of your campaign won't take place at lv 20, and he even said he wouldn't recommend it. Frankly, if we're taking Rogue at all, I wouldn't recommend multiclassing further. Think of it this way: the Soradin is a build that specializes in Divine Smite, but if we're taking levels of Rogue, we've already fallen behind on that front. Better to focus on what we aren't already behind on.
For your Rogue subclass, I'd recommend either Swashbuckler (more reliable Sneak Attacks, a nice bonus to Initiative), Arcane Trickster (increase your spell slot progression by the equivalent of 2 Paladin levels, pick up some nice cantrips [you want Minor Illusion, and Booming Blade will be nice until you get Extra Attack], and you will be able to get your choice of Shield and Find Familiar [not both though, due to spell school restrictions]), or Assassin (about to explain why next paragraph). NOTE: if you take Arcane Trickster, don't worry about your INT stat. It's not a multiclass requirement, and you should pick spells that don't rely on it (no attack roll, save, etc.), like Shield, Disguise Self, etc.
Despite what I said earlier about Assassin not being very good, if you're only taking 3 levels of it, that doesn't matter as much. It's mainly bad due to having borderline unusable abilities at levels 9 and 13, an the other abilities being very situational. However, if we only take 3 levels, that won't matter at all. The 3rd-level ability, despite being very situational, is actually really good if you can get it to go off, which you can sometimes do through strategic roleplay outside of combat (don't expect to be able to use it in a dungeon-crawl though).
Frankly, no matter which Rogue subclass you take (if any), I wouldn't go more than 2 or 3 levels. Paladin is a really strong class, considered to be the best martial class by a lot of people. The more Paladin you do, the better.
The build that I showed in my first reply, where I took Variant Human with Alert, took Assassin Rogue 3, then went straight Vengeance Paladin from there should actually be a moderately good build (I think that it should be better than most builds that are aren't optimized). Taking a Rapier should be your best bet, and start using a Shield when you become proficient when you take Paladin 1. Stick with Light Armor the whole way. It's probably on the weaker side if your party is full of optimizers, or the stronger side if no one else optimizes.
Since for some reason I can't edit this reply (not sure why not), I'll just put my would-be edit in a new reply.
Basically, what I'm trying to say is that the part that makes the Assassin Rogue/Paladin multiclass somewhat dubious is that the Rogue part and Paladin part don't fit together that well, not that Assassin isn't great. The Assassin isn't a great subclass, but it offers more synergy with Paladin than any other subclass.
In other words, if you really want to multiclass Rogue/Paladin, Assassin should be fine. If anything, the main difference between the subclasses (in this multiclass) is that Assassin will be more flavorful than the others. Assassinate has a good amount of Synergy with Paladin. Swashbuckler has a tiny bit of Synergy (literally just the fact that it uses CHA). Arcane Trickster has even less. If you want to play a Rogue/Paladin, feel absolutely free to take Assassin. You will, however, have abilities that feel like you just delayed the Paladin ones by 3 levels in exchange for some stuff you'll rarely use in combat.
In fact, your character concept doesn't even need to be a Paladin. You can be a straight-class Rogue working for a divine master without feeling the need to take Paladin and/or Cleric at all. Especially since you're serving a non-good god, perhaps the flavor of an Arcane Trickster would be even better for your concept without any multiclassing at all. Remember, to serve a god, you don't have to be a Paladin (or a Cleric) at all! People assume that a Paladin is a "champion of a god" (because that's what they were in previous editions), but if you read the flavor text in the 5e PHB, it just says that they *can* be in service to a god. They're actually supposed to be in service to an "ideal," which is chosen by their subclass.
I'm just trying to say that you don't HAVE to be a Paladin to fulfill your concept. You don't have to be a Rogue to fulfill your concept. If I were to play as a Rogue/Paladin, I'd take 3 levels of Assassin as my Rogue subclass, and then have fun roleplaying as a divinely-inspired assassin, who specializes in taking people by surprise. It seems like a fun gimmick to have, and if your DM will let you pull off the Assassinate ability every once in a while, that would be really fun to do. Just don't get overly attached to the idea of a certain class or class(es). You don't need to be a Rogue to be sneaky and assassinate people. You don't need to be a Paladin to fight for a god. If you wanted, you could fulfill your concept by taking 2 levels of Rogue and then going Trickery Cleric, with Kelemvor as your god. You could be any type of Rogue with a couple levels of Fighter and maybe the Acolyte Background or Magic Initiate (Cleric) feat. You could play a straight Rogue with the Acolyte background. I've actually played a Rogue who was a ninja specializing in gathering intelligence on behalf of the Pope of Pelor, and I was just a standard Human Arcane Trickster, with no multiclass.
What I'm trying to say is, essentially, try to be flexible. Feel free to take Assassin. Don't feel like you can't take Assassin. Don't feel like you have to take Assassin. Don't feel like you have to take Rogue. Don't feel like you have to take Paladin. Feel free to take whatever you want. In the end, you just have to roleplay as the character you're visualizing in your concept, and create a build with abilities that let you do what you imagine him doing.
Building one of these myself so thought I'd leave this here for other lurkers.
Does about 309 damage with action surge and GWM bonus attack. Or ~150 damage without them. Also has all the utility of paladin and bard spells.
Requirements: 13 Str, 13 Dex, 13 Cha
Stats: Standard Array: Dex 15, Con 12, Str 13, Cha 14, Wis 10, Int 8. If you're using Tasha's rules add +1 to Dex and +2 to Cha. (Low con won't be the worst as Shadar-Kai get resistance to everything after teleporting).
Race: Shadar-Kai (teleport guarantees surprise, meditate and trance recovers spell slots in a short rest)
Feat: GWM. You're not taking it for the +10 bonus damage per hit, you're taking it for the bonus attack you can get when you crit
Build is: Paladin 4 / Assassin 4 / Fighter 2 / Swords Bard 10
Basic premise is you use a Rapier to proc sneak attack/assassinate. It's a melee weapon so can still use with GWM to get the extra attack but you won't get the +10. This also means you don't have to take the GWM penalty on attack rolls.
You take care blind fighting / defence / duelling fighting styles, but defence seems the better option.
Can proc surprise in heavy armour if you teleport but it'll use your bonus action, or use a breastplate and stealth before battle to use your bonus action to attack.
You also have an extra attack through your bard sub class and get a lot more spells as a bard for smites. You get guaranteed surprise with teleport and if you can avoid using it to get surprise you'll get a bonus attack. All your long rest things like spells and teleports recover on short rest with Shadar Kai trance so you'll never run out.
Order of build is:
Paladin 2, Assassin 4, Fighter 2, Paladin 2, Bard 10