Leonardo, Sewer Samurai + Solemnity + Grinding Station + Shield Sphere

Leonardo, Sewer Samurai

Solemnity

Grinding Station

Shield Sphere

How it works

1. Activate Grinding Station by tapping it and sacrificing Shield Sphere.
2. Cast Shield Sphere from your graveyard by paying 0. It will not enter with a finality counter on it due to Solemnity.
3. When Shield Sphere enters, Grinding Station triggers, untapping Grinding Station.
4. Repeat.

This looping engine turns a humble zero-mana artifact into an unstoppable milling machine by exploiting a clever rules interaction. While Leonardo, Sewer Samurai normally brands anything pulled from your graveyard with a finality counter, Solemnity’s static ability steps in to prevent those counters from ever being placed. This allows you to cast Shield Sphere over and over again from the graveyard for free. Every time it enters the battlefield, Grinding Station's triggered ability untaps it, letting you sacrifice the sphere right back to the station to mill away your opponents' libraries card by card.