Integral

When Integral enters the battlefield, put X charge counters on it. Sacrifice Integral if it no longer has
charge counters.
{x}{t}: Add X*X colorless mana to your mana pool,
where X is the amount of charge counters on
Integral.
Lose X minus 1 mana at the end of each upkeep,
but unspent mana is kept each turn, where X is
the amount of charge counters on Integral.