Marchesa, the Black Rose, Time Sieve, and Myr Battlesphere

Prerequisites

• Marchesa, the Black Rose on the battlefield
• Time Sieve on the battlefield
• Myr Battlesphere on the battlefield
• You do not have the highest life total, or are tied for the highest life total
• Myr Battlesphere does not have summoning sickness
• You control at least four other artifacts

Steps

1. Declare Myr Battlesphere as an attacker, attacking the opponent with the most life or tied for the most life
2. Myr Battlesphere's dethrone ability triggers, putting a +1/+1 counter on it
3. Activate Time Sieve by tapping it, sacrificing Myr Battlesphere and four other artifacts you control
4. When Myr Battlesphere dies, Marchesa's second ability triggers, causing you to return Myr Battlesphere from your graveyard to the battlefield at the beginning of your end step
5. Resolve the Time Sieve ability, causing you to take an extra turn after this one
6. At the beginning of your end step, Marchesa triggers, causing you to return Myr Battlesphere from your graveyard to the battlefield
7. When Myr Battlesphere enters the battlefield, it triggers, creating four 1/1 Myr artifact creature tokens
8. Repeat each turn

Results

• Infinite turns