Anticausal Vestige + Cloudstone Curio + Dack's Duplicate

Anticausal Vestige

Cloudstone Curio

Dack's Duplicate

How it works

1. Cast Dack's Duplicate by paying its mana cost. Choose to have it enter as a copy of Anticausal Vestige.
2. When Dack's Duplicate enters, Cloudstone Curio triggers, returning Anticausal Vestige from the battlefield to your hand.
3. When Anticausal Vestige leaves the battlefield, it triggers, causing you to draw a card and and put Anticausal Vestige from your hand onto the battlefield.
4. When Anticausal Vestige enters, Cloudstone Curio triggers, returning Dack's Duplicate from the battlefield to your hand.
5. When Dack's Duplicate leaves the battlefield, it triggers, causing you to draw a card and put Dack's Duplicate from your hand onto the battlefield as a copy of Anticausal Vestige.
6. Repeat from step 2.

This ingenious loop relies on Dack's Duplicate entering the battlefield as a copy of Anticausal Vestige, turning itself into a duplicate of the latter creature with its unique departure and entry triggers intact. Because Cloudstone Curio watches for nonartifact permanents entering the battlefield, each time either creature enters, the other is bounced back to your hand, triggering the leaving-the-battlefield ability to draw a card and instantly redeposit the bounced permanent. By continually ping-ponging these two permanents back and forth between the battlefield and your hand, you fuel an endless cycle of leaves-the-battlefield and enters-the-battlefield events.