A Serial Killer is a player whose goal is to be the last player alive. They are aligned with themselves (meaning they have no allies) and have a factional kill at Night like the Mafia. Depending on the flavor, SKs may also be called Cannibals, Psychopaths, or Arsonists (note that Arsonist has since grown to describe a unique role).
Most moderators will not allow Towns or Mafias to win while a Serial Killer is still alive.
Serial Killer is the most difficult standard faction to win as, since being the sole survivor requires the player to dodge all of the Town's lynches and the Mafia's Night-kills. Thus, they are generally given a boost of some kind, depending on the game.
- Serial Killers are often awarded the win if all players die, typically done by wording the win condition akin to "you win when all other players are dead, whether you are alive or not".
- Serial Killers are often given One-Shot or unlimited Bulletproof. This stymies attempts to kill the SK by the Mafia or Vigs, if temporarily.
- Serial Killers have also been seen with investigation immunity like Godfathers, or Tracker/Watcher immunity like Ninjas.
In very complex games, Serial Killers can be complex roles unto themselves that just happen to have a factional kill and a self-aligned win condition.
Serial Killer, as a self-aligned third party, is considered Normal on mafiascum.net.
A standard Serial Killer has no additional powers, other than a night kill. Other roles or modifiers can be added, however, but they need to be shown when the SK flips. For example, a Serial Killer that gives an "innocent" result to Cops (and only Cops) is called an Investigation-Immune Serial Killer.
A Serial Killer's kill is considered factional, so if investigated by a Role Cop or Vanilla Cop, SKs (with no further powers) should return a "Vanilla" result. Serial Killers traditionally kill with knives, so show up as not having a gun to a Gunsmith investigation - note that all deaths should still have the same generic Kill Flavor.
Use and Power
Serial Killer exists to ratchet up the death count per Night and raise the swing of the game tremendously due to the SK's independent motivation. These are somewhat desirable in fairly stable Large games, but in role madness or smaller games SKs tend to lead to uncomfortable situations where their actions play a disproportionate role in deciding the game. This can be mitigated somewhat by including a Vigilante instead.
If you draw Serial Killer, do not claim NK-Immune Miller Vig. Although since that meme has appeared, some moderators actually have included that very role in their setups... Nonetheless, you are usually best off not claiming to be a Vigilante if you are a Serial Killer unless you are incriminated by a Tracker or Watcher result.