Time Sieve + Myr Battlesphere + Conjurer's Closet + Thopter Spy Network

Time Sieve

Myr Battlesphere

Conjurer's Closet

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, Conjurer's Closet triggers, blinking Myr Battlesphere.
3. When Myr Battlesphere enters the battlefield, its first ability triggers, creating four 1/1 Myr artifact creature tokens.
4. Activate Time Sieve by tapping it, sacrificing the Thopter and the four Myrs, causing you to take an extra turn after this one.
5. Repeat each turn.