Bound Servant

When Bound servant enters the battlefield, put a binding token on an artifact you control.
At the beginning of your upkeep, if you control a permanent with a binding token on it, put a
+1/+1 counter on Bound Servant.
At the beginning of your end step, if you don't
control a permanent with a binding token on it, sacrifice a creature and Bound Servant deals
damage to each player equal to its power