The Night's Watch. Non-Loyal.
Event. Cost: 0.

Dominance Action: Choose a character with the highest printed cost among characters you control. Sacrifice that character to choose a character an opponent controls and discard it from play.

Victor Garcia
Oberyn's Revenge #86.

Link: Decklists

Mutiny At Craster's Keep

Rules FAQ:

mplain 176
If I have no characters can I still play this event? — Statusunquo 1
No. Sacrificing a character is a cost ("do X to do Y"), if you cannot pay the cost, then you cannot play the event. — mplain 176