Provoking Hydra

Provoking Hydra enters the battlefield with X +1/+1 counters, where X is the damage dealt this turn.
When Provoking Hydra attacks or blocks, double the number of +1/+1 counters on it.
Provoking Hydra has trample and menace as long as there are five or more +1/+1 counters on it.