Fire-filled Trench
The Flame of the West#48 (x3/x2)
Location
2 (3)
Forced: When a player plays an event that would cancel the effects of a treachery card just revealed from the encounter deck, cancel the effects of that event. Then, discard Fire-filled Trench.

...as the trenches were made each was filled with fire, though how it was kindled or fed, by art or devilry, none could see. -The Return of the King