Can a Rogue PC teach an NPC to perform Sneak Attack?

Question

Important Note: I am aware of this post regarding NPC training but it failed to answer my question and the top answer has some holes.

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I want to run a heavily player-based, sandbox campaign (I am aware of the difficulties) and to help the players get started I decided to use Waterdeep: Dragon Heist as a way for them to get experience and money.

With that said I decided to give my players infinite choices (essentially I allow them to do as much as they can physically and mentally achieve). Consequently one of the most engaged players in the party, a Rogue level 4 (soon to be 5), decided he wanted to start a hitman business.

He managed to steal a bank and he used that as a way to disseminate a message via a local newspaper agency. The message advertised the hitman business and included directions for when and where to meet him if interested.

That much about the backstory. Now, the issue is that he wants to "train" NPCs (Bandits) to turn them into Assassins.

He told me he wants them to be able to use Sneak Attack (the Rogue's ability) but he also wants their Dexterity and Charisma modifiers to be higher than normal.

I was wondering, is there an official ruling that can assist me with NPC progress (type change more specifically)

If so, what are the limitations/prerequisites for that to happen?

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At the beginning of the post I linked a very similar thread. Though it failed to answer my question so I decided to repost.

I should note that the aforementioned post did not answer the question Can it be achieved, if yes how? I am trying to find a way to change an NPC's type from Bandit to Rogue. Another issue with the answer is that the player is not a trainer/teacher in any way. He has never trained anyone in his entire life which I imagine is a setback. Then, the answer states:

So, provided your PC is sufficiently skilled to offer "special" training, it would seem that they can impart some level of skill to the peasants.

In what level can a player be considered sufficiently skilled to offer training (as a mean to change the NPC's type)?

What is 'some level of skill'? Does this mean that an NPC cannot learn the Sneak Attack ability or does it mean that there is going to be a significant setback?

Note: As there has been confusion regarding what it is specifically that I am asking: I am asking for a way for a PC to change an NPC's 'class'/type. In my case from Bandit to Rogue. I am looking for personal experiences with similar scenarios using official ruling, if possible. It is true that I can try and come up with a system myself but I want to know if a system like that already exists.

Answer 1

The Unearthed Arcana Sidekicks rules allow an NPC to become like a Rogue

As Theik points out in their answer, the rules don't really offer any way to do this in the published books which treat NPC/monster stat blocks as immutable after they are created because they aren't really designed to be relevant for long.

However, in UA Sidekicks it provides a method for a DM to convert any friendly creature CR1 or below into an NPC with pseduo-class levels and advancement.

They give three "classes" that the Sidekick can take: Warrior, Expert, and Spellcaster. Expert is the rogue-like class, but unfortunately does not come with Sneak Attack as an option even with advancement.

However, it would allow you to change the NPC from Bandit to sort-of Rogue in a way that is designed not to overshadow or step on any PC toes.

Of course it is worth noting that, as UA, this is playtest material so may have play issues. But if a DM was looking to make this work, they could do much worse than using this as a starting point (if not just using it as-is).

Answer 2

No, there are no official rules for this

You are entirely in homebrew territory now. There are rules in the DM manual for making monsters and calculating their CR, but that's as far as the rules go. You're trying to allow players to turn monsters (NPCs) into other monsters (upgraded NPCs), which is not something the rules support. If you want a Bandit with Sneak Attack, you make a bandit, add sneak attack and then recalculate the CR. How they got Sneak Attack in the first place is not something the manual concerns itself with, that part of "NPCs/Monsters earning skills" is entirely homebrew turf.

As far as the rules are concerned, that NPC bandit will forever be a NPC bandit. You can, as a DM, decide that that bandit can start earning PC levels by gaining experience, but that is not something the rulebook goes into detail on, normally the experience NPCs earn just vanishes into thin air.

If you want to include this, you might be able to start using the NPC as a sidekick. However, the way you describe the player, it sounds like they will end up having a whole army of sidekicks, which kind of defeats the point of the sidekick system in the first place if you ask me. None of the sidekick classes have sneak attack so you'd still have to come up with your own implementation of the sidekick system if that is your intention.

Do be warned however that every NPC that tags along will take a share of the experience of all players. If one player has several tag-along sidekicks and they're all draining the party exp pool, the rest of the party might not like this very much.

Answer 3

There are some basic rules for PCs learning new proficiencies and languages on page 134 of Xanathar’s Guide to Everything, you might look at this when determining HOW to teach these NPCs, perhaps increasing the time required to learn since sneak attack is a useful combat skill, rather than a proficiency.

Additionally, if you need to determine wether a PC is qualified as a teacher, perhaps they can gain proficiency in teaching by following the aforementioned training rules.

Hope this helps somewhat. As far as a definite answer to IF changing an NPC is allowed or not, that’s up to you. I would allow it if the player puts in significant time/resources, but that’s just me.