Pet Hydra

Pet Hydra enters the battlefield with X +1/+1 counters on it .
Whenever Pet Hydra is dealt damage, if you control an Aggrol planeswalker, if it survives the damage, put that many +1/+1 counters on it.
Pet Hydra has menace as long as you control an Aggrol planeswalker.
Made for the Planeswalker's Journey contest.