Time Sieve + Myr Battlesphere + Soulherder + Thopter Spy Network

Time Sieve

Myr Battlesphere

Soulherder

Thopter Spy Network

How it works

1. At the beginning of your upkeep, Thopter Spy Network's first ability triggers, creating a 1/1 Thopter artifact creature token.
2. At the beginning of your end step, Soulherder's second ability triggers, blinking Myr Battlesphere.
3. When Myr Battlesphere enters the battlefield, it and Soulherder's first abilities trigger.
4. Resolve the Soulherder trigger, putting a +1/+1 counter on it.
5. Resolve the Myr Battlesphere trigger, creating four 1/1 Myr artifact creature tokens.
6. Activate Time Sieve by tapping it, sacrificing the Thopter and the four Myrs, causing you to take an extra turn after this one.
7. Repeat each turn.

This loop transforms a modest start-of-turn engine into an endless chain of extra turns. Each cycle begins with Thopter Spy Network generating a fresh artifact token during your upkeep to help pay for later sacrifices, while its secondary ability even rewards your growing robot army with card draw when they deal damage. The real magic happens during your end step, where Soulherder repeatedly blinks Myr Battlesphere to flood the board with new Myr tokens. Armed with this steady supply of fresh metal, Time Sieve easily finds five artifacts to sacrifice every cycle, securing infinite turns to safely close out the game.