Mayin Nerool

+2: Add X mana in any combination of {g} and/or {u} to your mana pool, where X is the number of +1/+1 counters on creatures you control.
-3: Draw X cards, where X is the number of +1/+1 counters on creatures you control.
-4: You get an emblem with "Each creature you control enters the battlefield with an additional +1/+1 counter on it."