A Normaliser (or Normalizer) is a player who can target another player at night to change their power, turning them into the nearest Normal role equivalent. For example, an Insane Cop would be turned into a Sane Cop, or a CPR Doctor would be turned into a normal Doctor. If there are no similar Normal roles (for example: Framer, Redirector or Cult Leader), the role is turned into Vanilla.
Normalisers can be of either alignment and are tricky to balance due to the swing it creates. Before you put one in a game, you need to know exactly what it would do to every other role in the game.
Use and power
A Normaliser can be very powerful if it is able to (as town) find certain power roles that would become more useful - or (as scum) find and minimise powerful roles. Because of this power, it's best to limit the amount of shots the Normaliser has.