Regal Ancestor Spirit

{1}{g}{u}{t}: Sacrifice a creature, put X +1/+1 counters on Regal Ancestor Spirit. where X is equal to the sacrificed creature's power.

Remove X+1/+1 counters from Regal Ancestor Spirit: You may cast a spell
with mana value of X or less where X is equal
to the number of counters removed this way, without paying it's mana cost.