Necrosis Hydra

Convoke, trample
Shamans and zombies you tap to convoke Necrosis Hydra pay for {2} instead of {1}.
When Necrosis Hydra enters the battlefield, put the top X cards of your library into your graveyard, then put a +1+1 counter on Necrosis Hydra for each creature card in your graveyard.
"Death is always in season."