Srek, the Plague Doctor

Ward—gain 2 poison counters.
At the beginning of combat on your turn,
you may have another target creature you
control gain +X/+0, menace, and haste until
end of turn, where X is equal to the number
of poison counters your opponents have.
That creature is sacrificed at the beginning
of the next end step. If that creature failed
to deal damage to an opponent, you get
a poison counter.