Forbidden Droplet (Secret Rare)

Pendulum Effect: Once per turn: You can target 1 face-up monster you control; it gains ATK equal to the difference between the number of cards in the Extra Decks x 100, until the end of this turn (even if this card leaves the field).
Monster Effect: Gains ATK during your turn only, and gains DEF during your opponent's turn only, each equal to the difference between the number of cards in the Extra Decks x 200. If this card attacks, it is changed to Defense Position at the end of the Battle Phase. If this card in the Monster Zone is destroyed: You can place this card in your Pendulum Zone.