Leonardo, Sewer Samurai + Solemnity + Crimson Kobolds + Yahenni, Undying Partisan

Leonardo, Sewer Samurai

Solemnity

Crimson Kobolds

Yahenni, Undying Partisan

How it works

1. Activate Yahenni 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 recursive loop turns the humble Crimson Kobolds into an engine of endless sacrifices by leveraging Leonardo, Sewer Samurai to repeatedly cast them from your graveyard for zero mana. While Leonardo would normally stamp these returning creatures with a finality counter to exile them upon death, Solemnity acts as a crucial safety valve, blanket-banning all counters from being placed on permanents so the Kobolds can return cleanly every single time. Meanwhile, Yahenni, Undying Partisan sits back and feasts on the endless parade of vanishing Kobolds, happily growing larger while happily granting itself indestructible to anchor the whole loop together.