Like any other class a Neutral needs to serve a purpose. In general the purpose of a Neutral is to make there more than 1 reason for someone to want to trick you. That leads to classes such as Scorned and Fool. However then there comes other purposes such as adding non-hostile wincons that make it so you can know someone’s class but still not know if they are trustworthy. That leads to classes such as Alchemist and Mercenary.
One thing to understand about Neutrals is to explain something that they are not. They are not the Neutral Killer. Confused?
Unlike all other Neutrals the NK stands in the way of a win for BD or Unseen. That and there is no wiggleroom in what counts as a win. WIthout that ambiguity you lose the 2nd aspect of the neuts and what you are left with (the basic “eliminate all other factions”) makes the NK closer to the Informed Minority than a Survivor or Scorned. When you are designing a Neutral you should never make an NK. That means that they need to be able to win with at least 2 of the factions (Unseen/Cult, BD and NK) in order to work.
Beyond neutrals in general any given Neutral can serve it’s own purpose. For example the Fool makes vote for class and process of elimination less effective while Scorned makes it far easier to defend yourself from an accusation as scum. The best Neutrals have a clear purpose such as this one.
A good purpose is usually a psychological one that has to do with the POSSIBILITY of the class rather than an interaction with the class itself. For example the Alchemist and Mercenary gives a reason to not execute all Neuts you find as they can be more helpful than some BD. And the Scorned makes accuser that much more suspicious in the early game where other scum accusing isn’t worth it. This is why the Inquisitor is relatively bland. He has one purpose: Keep the Sorcerer in check. His interaction isn’t that interesting for anyone besides himself and the Sorcerer so no one cares about his existence making the class irrelevant.
This is why Visitor Winconditions and other winconditions that don’t inherently harm another faction tend to be boring.
The next thing is to make your wincondition as simple as possible. You should be able to describe it in a single sentence. “Survive” “Lynch player X or Y” “Same as X” “Become king” You get the idea. The more you can accomplish the goal of the classes existence through emergent propriety’s rather than complex win conditions the better.
For example take the Survival wincondition. It has the straightforward part of making you want to play nice with everyone at the same time, however it also has the emergent property of creating a feedback loop. The less day’s pass the less likely you are to die. Therefor a class with this win-condition speeds up the game.
Finally, you have the ability’s. Yes up to this point you shouldn’t have decided on a single power. Think about what the class is trying to accomplish. The ability’s should first of all be directly tied to either the wincondition or one of its emergent property’s.
Alchemist:
Stoneskin - Survive (direct)
Heal - Play nice (emergent)
Kill - Speeds up game (emergent)
That doesn’t mean that the ability has to further your goals. Negative utility’s can exist.
Fool:
Poor Fellow - Getting lynched (direct)
^^^ That is a perfectly valid justification for having the ability in the game. However while the ability doesn’t need to help you it does need to be directly tied to the win condition.
Take a faction check on Scorned for example. What purpose would that serve? It would probably help, however it wouldn’t necessarily get people lynched (it could even stop it if you confirm someone that was going to be lynched). And it only gives the Unseen more reason to kill you. It would probably still be a buff but it doesn’t have to do with the wincondition like a heal or kill does.
TLDR:
1: Wincondition needs to serve a greater purpose
2: Wincondition needs to not make it another faction
3: Simple winconditions are better. Use emergent property’s to get complex interaction
4: A psychological effect is better than a mechanical one
5: Ability’s need to serve the Wincondition