Flying
{1}{U}: Mirror-Mad Phantasm's owner shuffles it into their library. If that player does, they reveal cards from the top of that library until a card named Mirror-Mad Phantasm is revealed. The player puts that card onto the battlefield and all other cards revealed this way into their graveyard.
If another creature (such as Necrotic Ooze) gains Mirror-Mad Phantasm’s activated ability, its owner reveals cards until they reveal a card named Mirror-Mad Phantasm.
If no card named Mirror-Mad Phantasm is revealed (possibly because it was a card copying Mirror-Mad Phantasm or it was a token), all cards from that library will be put into their owner’s graveyard.
You can only activate the ability if you control Mirror-Mad Phantasm, even if you don’t own it.