The incarnation of rage

Whenever you take one or more damage put
+1/+1 counter on {The incarnation of rage}.
You may pay {p/r} rather then pay {r} for casting
spells (only one time to spell)
Remove +1/+1 counter from [ ]: [ ] gains +X/+X
until end of turn where X is half of number+1/+1
counters on [ ] rounded up