Xenomorph Alpha

Acid Blood (If a creature deals any amount of combat damage to this creature, it gains a - 1/-1 counter.)
Swampwalk (This creature can't be blocked as long as defending player controls a Swamp.)
At the beginning of your upkeep, return target Xenomorph creature card from your graveyard to the battlefield.
At the beginning of each opponent's upkeep, that player sacrifices a creature