Eleg, The Debt Collector

Whenever your opponents cast a spell, create a
debt counter under that player's control.
At the beginning of each opponents end step,
they may pay {1} per debt counter to remove it.
Then, you may add {1} to your mana pool at the
beginning of your next main phase for each debt
counter opponents have.
{4}, Remove a debt counter from target player:
Draw a card.