D/D Savant Galilei

You cannot Pendulum Summon monsters, except "D/D" monsters. This effect cannot be negated. Once per turn, during your Standby Phase: Increase this card's Pendulum Scale by 2 (max. 10), then destroy all monsters you control with a Level less than or equal to this card's Pendulum Scale, except "D/D" monsters.

During either player's turn: You can discard this card, then target 1 "D/D" or "Dark Contract" card you control; return it to the hand. You can only use this effect of "D/D Savant Galilei" once per turn.