Aether Infinitum

Aether Infinitum enters the battlefield with X refill counters on it. Whenever a player uses any amount of {e}, they may tap Aether Infinitum and remove a refill counter from it. If they do, they get all expended {e} back from that turn. Aether Infinitum untaps during each player's upkeep.
Recharge Y, {t}: Spend Y {e}. Put Y refill counters on Aether Infinitum. You may only do this at any time you could cast a sorcery.
When no refill counters remain, exile Aether Infinitum.