Mortuary + Umbral Collar Zealot + Phyrexian Walker + Bolas's Citadel

Mortuary

Umbral Collar Zealot

Phyrexian Walker

Bolas's Citadel

How it works

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

This ingenious loop turns a free artifact creature into an endless engine of card selection and graveyard recycling. With Bolas's Citadel granting you the vital ability to cast spells directly from the top of your library, you can repeatedly deploy Phyrexian Walker for zero mana while Mortuary quietly catches it upon death and tucks it right back onto your library's peak. Meanwhile, Umbral Collar Zealot acts as the catalyst, letting you sacrifice that same creature to surveil the top of your library and seamlessly restart the cycle.