Echocasting Symposium + Capture of Jingzhou + Timeless Witness Combo

Timeless Witness on the battlefield.

Echocasting Symposium in exile (Echocasting Symposium exiled by its paradigm ability in exile).

Capture of Jingzhou in hand.

each turn available

Cast Capture of Jingzhou by paying its mana cost, causing you to take an extra turn after this one.

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.

Resolve the copy, creating a token copy of Timeless Witness

When the Timeless Witness token enters, it triggers, returning Capture of Jingzhou from your graveyard to your hand.

Repeat.

Infinite turns

Lock