Dream Chisel + Ugin, the Ineffable + Cloudstone Curio

Dream Chisel

Ugin, the Ineffable

Cloudstone Curio

How it works

1. Cast the creature card in your hand for its morph or megamorph cost by paying 0, putting it onto the battlefield face down as a 2/2 creature.
2. When the creature enters the battlefield, Cloudstone Curio triggers, returning another creature card with morph or megamorph from the battlefield to your hand.
3. Repeat.