Harsenius, Lord of Hydras

Trample
Harsenius, Lord of Hydras enters the battlefield
with X +1/+1 counters. Each time a creature
spell is cast, place a +1/+1 counter on Harsenius.
Each time an instant or sorcery card is cast,
put two +1/+1 counters on Harsenius.
Each time a Planeswalker spell is cast, double the number of +1/+1 counters on Harsenius.