You can target 1 other card you control; destroy it, and if you do, add 1 "roid" card from your Deck to your hand. During damage calculation, if your "roid" monster battles: You can send 1 "roid" monster from your Deck to the GY; switch the original ATK and DEF of your battling monster during the damage calculation only. You can only use each effect of "Megaroid City" once per turn. You cannot Special Summon monsters from the Extra Deck, except Fusion Monsters, the turn you activate either of this card's effects (even if this card leaves the field).