Leonardo, Sewer Samurai + Solemnity + Ravenous Intruder + Phyrexian Walker

Leonardo, Sewer Samurai

Solemnity

Ravenous Intruder

Phyrexian Walker

How it works

1. Activate Ravenous Intruder by sacrificing Phyrexian Walker.
2. Cast Phyrexian Walker from your graveyard by paying 0. It will not enter with a finality counter on it due to Solemnity.
3. Repeat.

This clever loop turns the graveyard into a virtually limitless workshop using Leonardo, Sewer Samurai to repeatedly cast Phyrexian Walker for zero mana. Solemnity is the linchpin of the interaction, overriding the finality counters that would normally exile your creatures and allowing the Walker to return endlessly. Once it's back in your graveyard, you can sacrifice it to Ravenous Intruder to pump it to astronomical proportions while generating an endless stream of sacrifice and death triggers.