Time Sieve + Myr Battlesphere + Soulherder + Gandalf the White

Time Sieve

Myr Battlesphere

Soulherder

Gandalf the White

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 and Soulherder's first ability trigger twice.
3. Resolve both Soulherder triggers, putting two +1/+1 counters 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 elegant loop leverages Soulherder to repeatedly blink Myr Battlesphere at the beginning of each end step, flooding the board with artifact creatures. Because Gandalf the White is on the battlefield, the artifact nature of the resulting Myr tokens and Myr Battlesphere itself causes its entry triggers—and Soulherder's counter-generating triggers—to double, quickly yielding an overabundance of disposable artifacts. You can then cash in five of those tokens to Time Sieve, sacrificing them to immediately secure an extra turn and lock the game down indefinitely.