Brudiclad, Telchor Engineer, There and Back Again, and Time Sieve

Prerequisites

• Brudiclad, Telchor Engineer on the battlefield
• There and Back Again on the battlefield
• Time Sieve on the battlefield
• There and Back Again has exactly two lore counters on it

Steps

1. At the beginning of your precombat main phase, There and Back Again triggers, creating a legendary 6/6 Smaug creature token, and causing you to sacrifice There and Back Again
2. At the beginning of your combat phase, Brudiclad triggers, creating a 2/1 Phyrexian Myr artifact creature token, then causing all tokens you control to become copies of the Smaug token
3. Put all but one Smaug token into your graveyard due to the legend rule
4. When the Myr dies, it triggers, creating fourteen Treasure tokens
5. Activate Time Sieve by tapping it and sacrificing five Treasures, causing you to take an extra turn after this one
6. Repeat from step 2 each turn

Results

• Infinite turns