You can only activate 1 “Magical Meltdown” per turn.
(1) When this card is activated: You can add 1 “Aleister the Invoker” from your Deck to your hand.
(2) If you activate a card/effect that includes an effect that Fusion Summons a Fusion Monster, that activation cannot be negated, also your opponent cannot activate cards/effects when that monster is Fusion Summoned.