@killable is a command that allows players to be hit by other players, it's commonly used for fast build testing with other players or friendly PVP.
Using @killable[]
To use this command simply type @killable and you will allow targetting in your character from other players, to deactivate this feature just type it again, and you will be safe from other player's attacks.
Note that attacking a character that is with @killable activated with a basic attack will turn on the command on the attacker too, attacking with a skill won't activate it.