The Philosopher's Stone

{t}: Sacrifice a creature then put X charge
counters on The Philosopher's Stone, where X is
that creature's converted mana cost.
{t}, Remove any number of charge counters from
The Philosopher's Stone: Add {c} for each charge counter removed this way.
"In order to obtain something, there must be something
of equal value. It is the law of conservation in
alchemy. Back then, we believed that it was the truth
of the world." -Alphonse Elric