Boreal Hydra

Boreal Hydra enters the battlefield with X +1/+1 counters on it.
tribute X (As this creature enters the battlefield, an opponent of your choice may place X +1/+1 counters on it, where X is Boreal Hydra's power.)
When Boreal Hydra enters the battlefield, if tribute wasn't paid, it deals X damage to any target where X is its power.