Mortuary + Ravenous Intruder + Phyrexian Walker + Bolas's Citadel

Mortuary

Ravenous Intruder

Phyrexian Walker

Bolas's Citadel

How it works

1. Activate Ravenous Intruder by sacrificing Phyrexian Walker
2. When Phyrexian Walker dies, Mortuary triggers, putting Phyrexian Walker from your graveyard onto the top of your library.
3. Resolve the Ravenous Intruder ability.
4. Cast Phyrexian Walker from the top of your library by paying 0 life.
5. Repeat.

This clever loop centers around Bolas's Citadel, which grants you the crucial ability to cast spells directly from the top of your library by paying life instead of mana. With a mana value of zero, you can cast Phyrexian Walker for free whenever it reaches the top, while Mortuary ensures that whenever that same Phyrexian Walker is put into your graveyard from the battlefield, it immediately returns right back to the top of your library. To fuel this recycling engine, Ravenous Intruder acts as the sacrificial outlet, letting you pitch the artifact creature into the graveyard to grow its own power and trigger the entire infinite sequence anew.