The Tripper Mercury #DLCS-EN102

WaterMonster

When this card is Tribute Summoned: You can change all monsters on the field to face-up Attack Position. You can Tribute 3 monsters to Tribute Summon (but not Set) this card. If Summoned this way, while this card is on the field all monsters your opponent controls lose ATK equal to their original ATK. This card can make a second attack during each Battle Phase.