Xeno'Jiva

Flying, protection from colored spells.
Xeno'Jiva enters the battlefield with X +1/+1 counters on it. At the beginning of your upkeep
you can put a +1/+1 counter on Xeno'Jiva.
Remove any number of +1/+1 counters from
Xeno'Jiva: destroy target permanent that has
casting cost equal to the number of +1/+1
counters removed from Xeno'Jiva this way, you
can activate this ability only as a sorcery.