River Song, Conjurer's Bauble, Mechanized Production, and Time Walk

Prerequisites

• River Song on the battlefield
• Conjurer's Bauble on the battlefield
• Mechanized Production on the battlefield
• Time Walk in hand

Steps

1. At the beginning of your upkeep, Mechanized Production triggers, creating a token copy of Conjurer's Bauble
2. Cast Time Walk by paying its mana cost, causing you to take an extra turn after this one
3. Activate the Conjurer's Bauble token by tapping and sacrificing it, putting Time Walk onto the bottom of your library from your graveyard, and then causing you to draw Time Walk from the bottom of your library due to River Song
4. Repeat each turn

Results

• Infinite turns