Daervik, Draco-Sovereign

Flying
At the beginning of each opponents's upkeep,
that player sacrifices a creature for each Dragon
you control. Put a +1/+1 counter on Daervik,
Draco-Sovereign for each creature sacrificed this
way.
{x}, Remove X +1/+1 counters from Daervik: Put target Dragon creature in your graveyard with converted mana cost X or less onto the battlefield.
I don't do contracts or niceties. If you want to live, find another world.