Scrap Mastery, Codex Shredder, and Time Sieve

Prerequisites

• Scrap Mastery in the graveyard
• Codex Shredder on the battlefield
• Time Sieve on the battlefield
• each turn available

Steps

1. Activate Time Sieve by tapping it and sacrificing it and four other nontoken artifacts except Codex Shredder, causing you to take an extra turn after this one
2. Activate Codex Shredder's second ability by paying , tapping and sacrificing it, returning Scrap Mastery from your graveyard to your hand
3. Cast Scrap Mastery by paying , exiling all artifact cards from all graveyards, then causing each player to sacrifice all artifacts they control and return all artifacts exiled this way to the battlefield under their owner's control
4. Repeat each turn

Results

• Infinite turns