You may have this creature enter as a copy of any creature on the battlefield, except it's an Illusion in addition to its other types and it has "When this creature becomes the target of a spell or ability, sacrifice it."
Serum was once derived from Mirrodin's blinkmoths, offering visions of inspiration. Now it is pulled from Phyrexian inkmoths, yielding visions of perfection.
When this creature enters, create a number of 1/1 black Rat creature tokens equal to the number of opponents you have. {1}{B}, Sacrifice a creature: Target creature gets -2/-2 until end of turn.
Enchant creature an opponent controls When enchanted creature dies, exile cards equal to its power from the top of its owner's library. You may cast spells from among those cards for as long as they remain exiled, and mana of any type can be spent to cast them.
Flying Whenever this creature deals combat damage to a player, that player exiles a card from their hand. You may play that card for as long as it remains exiled. Sacrifice a Human: Regenerate this creature.