Saga of the Dragon Emperor

Target 1 Dragon monster you control; its ATK becomes doubled (until the end of this turn), then, if your opponent currently controls a Dragon monster, the activation of the targeted monster's effects cannot be negated for the rest of this turn. During your Main Phase: You can banish this card from your GY; Special Summon 1 of your Dragon Xyz Monsters that is banished or in your GY, in Defense Position. You can only use 1 "Saga of the Dragon Emperor" effect per turn, and only once that turn.