Rathax, the Unkillable

Trample, Indestructible
Other Hydras you control get +1/+1.
Rathax, the Unkillable enters the battlefield with
X +1/+1 counters.
Whenever Rathax, the Unkillable takes damage,
remove that many +1/+1 counters, then create a
token thats a copy of Rathax, the Unkillable,
that's not legendary, for each +1/+1
counter removed this way.
{4}, {t}: Put a +1/+1 counter on Rathax, the Unkillable.