Brainjacker Worm

Parasitize - Gain control of target non-artifact creature. (When this creature enters the battlefield,
put it under target non-artficact creature. While under
a creature, it cannot attack, be attacked, and block. It
can still be targetted by spells and abilities.)
At the beginning of your turn, before your draw
step, discard a card. If you can't, sacrifice Brainjacker Worm.