Echocasting Symposium + Eternal Witness + Temporal Manipulation

Echocasting Symposium

Eternal Witness

Temporal Manipulation

How it works

1. Cast Temporal Manipulation 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 Eternal Witness
4. When the Eternal Witness token enters, it triggers, returning Temporal Manipulation from your graveyard to your hand.
5. Repeat.