Arcanis, Sculptor of Planes

Whenever you cast an instant or sorcery spell,
you may exile it.
Whenever Arcanis, Sculptor of Planes attacks,
you may copy all spells exiled with it. If you do,
cast those spells without paying their mana costs.
At the beginning of your end step, if there are
four or more cards exiled with Arcanis, tansform
him.