Spellsponge

Flash
Whenever a player casts an instant or sorcery
spell, counter that spell. When it would enter the graveyard, instead exile it with Spellsponge and
put a reef counter on it.
At the beginning of your upkeep, if Spellsponge
has 3 or more reef counters on it, sacrifice it.
You may cast any number of spells exiled with Spellsponge without paying their mana costs.