Mortuary + Phyrexian Walker + Bolas's Citadel + Phantom Train

Mortuary

Phyrexian Walker

Bolas's Citadel

Phantom Train

How it works

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

This clever loop turns the zero-mana cost of Phyrexian Walker into an engine for endless triggers. Bolas's Citadel serves as the command center, allowing you to continually cast that free artifact creature straight from the top of your library while paying life instead of mana. Once played, Phyrexian Walker is fed directly into Phantom Train's sacrifice ability to animate the Vehicle and pump it up with a +1/+1 counter. That death immediately awakens Mortuary, whose static trigger quietly intercepts the Walker in the graveyard and stacks it right back onto the top of your library, perfectly poised for Bolas's Citadel to cast it all over again.