Time Sieve + Myr Battlesphere + Soulherder + Panharmonicon

Time Sieve

Myr Battlesphere

Soulherder

Panharmonicon

How it works

1. At the beginning of your end step, Soulherder's second ability triggers, blinking Myr Battlesphere.
2. Myr Battlesphere's first ability triggers twice and Soulherder's first ability triggers.
3. Resolve the Soulherder trigger, putting a +1/+1 counter on it.
4. Resolve both Myr Battlesphere triggers, creating eight 1/1 Myr artifact creature tokens.
5. Activate Time Sieve by tapping it and sacrificing five Myrs, causing you to take an extra turn after this one.
6. Repeat each turn.

This delightful loop spins out of control by turning your end step into an endless factory of mechanical minions and stolen time. At the heart of it, Soulherder repeatedly blinks Myr Battlesphere, but the real multiplier is Panharmonicon, which doubles the Myr tokens created on every single re-entry to easily feed the hungry maw of Time Sieve. While you are busy sacrificing those hordes to take infinite extra turns, Soulherder even happily grows larger with a +1/+1 counter each time a creature is exiled.