Mortuary + Phyrexian Walker + Bolas's Citadel + Yahenni, Undying Partisan

Mortuary

Phyrexian Walker

Bolas's Citadel

Yahenni, Undying Partisan

How it works

1. Activate Yahenni 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 Yahenni ability.
4. Cast Phyrexian Walker from the top of your library by paying 0 life.
5. Repeat.

This elegant loop transforms the ultimate artifact resource engine into an endless storm by exploiting free resource recycling. Bolas's Citadel allows you to cast cards directly from the top of your library while trading mana costs for life payments, which means Phyrexian Walker can be recast for zero life. Once it enters the battlefield, you use Yahenni, Undying Partisan's activated ability to sacrifice the artifact creature, sending it straight to the graveyard. That death immediately triggers Mortuary, which scoops the walker right back onto the top of your library where Bolas's Citadel is waiting to cast it all over again.