Time Sieve + Encroaching Mycosynth + Helm of the Host + Master of Waves

Time Sieve

Encroaching Mycosynth

Helm of the Host

Master of Waves

How it works

1. At the beginning of your combat phase, Helm of the Host triggers, creating a token copy of Master of Waves with haste.
2. When the Master of Waves token enters the battlefield, it triggers, creating a number of 1/0 Elemental creature tokens equal to your devotion to blue.
3. Activate Time Sieve by tapping it and sacrificing five creature tokens, causing you to take an extra turn after this one.
4. Repeat each turn.

By turning every nonland permanent you control into an artifact, Encroaching Mycosynth sets the stage for your non-artifact creatures to pull double duty as sacrifice fodder. This allows Master of Waves to serve as a massive token producer, as its enter-the-battlefield trigger fills your board with Elemental creatures scaled to your devotion to blue. Meanwhile, Helm of the Host ensures this engine is self-sustaining by churning out a fresh token copy of Master of Waves every single combat phase, providing the exact number of bodies needed. You can then feed those newly minted artifacts straight into Time Sieve, sacrificing five of them to chain infinite extra turns and completely lock your opponents out of the game.