Fairy Tail - Sleeper (OP05-EN007) [OTS Tournament Pack 5]

FLIP: You can Special Summon 1 monster from your hand.
During either player's turn, when your opponent activates a Normal Spell/Trap Card: You can Tribute 1 other monster; the activated effect becomes "Change 1 face-up monster your opponent controls to face-down Defense Position". You can only use this effect of "Fairy Tail - Sleeper" once per turn.