Echocasting Symposium + Returned Pastcaller + Time Warp

Echocasting Symposium

Returned Pastcaller

Time Warp

How it works

1. Cast Time Warp by paying its mana cost, causing you to take an extra turn after this one.
2. Move to your next turn. At the beginning of your precombat main phase, Echocasting Symposium's paradigm ability triggers, causing you to cast a copy of it from exile.
3. Resolve the copy, creating a token copy of Returned Pastcaller
4. When the Returned Pastcaller token enters, it triggers, returning Time Warp from your graveyard to your hand.
5. Repeat.