Leonardo, Sewer Samurai + Solemnity + Crimson Kobolds + Phantom Train

Leonardo, Sewer Samurai

Solemnity

Crimson Kobolds

Phantom Train

How it works

1. Activate Phantom Train by sacrificing Crimson Kobolds.
2. Cast Crimson Kobolds from your graveyard by paying 0. It will not enter with a finality counter on it due to Solemnity.
3. Repeat.

This loop is a masterclass in turning a card's drawback completely on its head. While Leonardo, Sewer Samurai normally brands anything pulled from your graveyard with a finality counter—exiling it if it would die—Solemnity steps in to prevent those counters from ever being placed in the first place. This lets you endlessly recur free fodder like Crimson Kobolds, which you can sacrifice to Phantom Train to pump its stats while feeding your graveyard. Because Solemnity nullifies Leonardo's counter restriction, the Kobolds can return to the battlefield over and over again, generating an endless stream of sacrifice, death, and trigger synergy.