Rast, Summoner of the Scum

At the beginning of your upkeep, put a black 1/1
crow creature token with infect and flying onto
the battlefield under your control.
{3}{b}: Put either a 1/1 black rat-, or a 1/1 black
zombie creature token onto the battlefield under
your control.
At the beginning of your endstep, you lose 3 life
unless you sacrifice a creature.