Deepmire Hydra

Deepmire Hydra enters the battlefield with X
+1/+1 counters on it.
As long as there are ten or more +1/+1 counters
on Deepmire Hydra, it has, "Whenever this
creature deals combat damage to a creature, exile
that creature. You may cast that card for as long
as it remains exiled, and you may spend mana as
though it were mana of any type to cast that
spell."