Time Sieve, Myr Battlesphere, and Debtors' Knell

Prerequisites

• Time Sieve on the battlefield
• Myr Battlesphere in the graveyard
• Debtors' Knell on the battlefield

Steps

1. At the beginning of your upkeep, Debtors' Knell triggers, returning Myr Battlesphere from your graveyard to the battlefield
2. Myr Battlesphere enters the battlefield, creating four 1/1 Myr artifact creature tokens
3. Activate Time Sieve by tapping it, sacrificing Myr Battlesphere and the four Myr tokens, causing you to take an extra turn after this one
4. Repeat each turn

Results

• Infinite turns