Subterror Behemoth Ultramafus

Card text

FLIP: You can change all other face-up monsters on the field to face-down Defense Position. You can only use this effect of "Subterror Behemoth Ultramafus" once per turn. When a face-up monster you control is flipped face-down, if you control no face-up monsters: You can Special Summon this card from your hand in Defense Position. Once per turn: You can change this card to face-down Defense Position.