Sheoldred's Assimilator is a rare Creature — Phyrexian Horror card from Alchemy: Phyrexia (YONE), collector number 10.
Menace Whenever Sheoldred's Assimilator enters or attacks, exile up to one target card from a graveyard. If a card is exiled this way, you may conjure a duplicate of that card into the top five cards of your library at random.