FLIP: You can target 1 Set monster your opponent controls; take control of it until your next End Phase. You can only use this effect of "Subterror Behemoth Voltelluric" 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.