This is the Trap Card that Skull Knight used:
REVERSE EFFECTOR
Normal Trap
Effect: You may activate this card when a set Monster that you control is targeted by an effect. Flip that Monster into Attack Position, and activate its Flip-Effect, if any. Then, send that Monster to the Graveyard.
Skull Knight used this Trap to activate the Flip-Effect of his Magical Merchant before Axel's Tri-Blaze Accellerator could destroy it.