The Borg Queen

Artifact creatures you control get +2/+2.
Whenever The Borg Queen enters or attacks, target opponent exiles cards from the top of their library until they exile a creature card. Assimilate that card. They put the rest on the bottom in a random order. (To assimilate a card, put it onto the battlefield under your control with a +1/+1 counter. It's a Borg artifact creature and loses all other creature types.)