Once in the game during Night, you may attempt to annihilate a player. An annihilated player is treated as being completely nonexistent for all purposes except win condition (an annihilated player counts as dead for wincon purposes).
Annihilation pierces protection and immunities that specifically protect against killing, since Annihilation isn't considered killing for action resolution purposes.
Annihilated players disappear without a flip (and can't be targeted by even Strong-Willed Coroners!), are removed from all PTs they have access to, don't allow backups to grab their roles, and aren't added to the Dead PT, for example.