Scour Hydra

Scour Hydra cost {x} less to cast where X is the
number of creatures on the battlefield.
Scour Hydra has trample as long as it's total
power and toughness is twenty or greater. (Both
power and toughness combined.)
At the beginning of your end step, put X +1/+1
counters on Scour Hydra where X is twice the
amount of damage dealt to Scour Hydra
this turn.