Nerotomean Hydra

Emerge {x}{x}{g} (You may cast this spell by sacrificing a creature and paying the emerge cost
reduced by that creature's mana value.)
Hexproof
You may sacrifice any number of creatures to
pay for Nerotomean Hydra's emerge cost.
Nerotomean Hydra enters the battlefield with X
+1/+1 counters on it.