Mortuary + Bolas's Citadel + Haywire Mite + Phantom Train

Mortuary

Bolas's Citadel

Haywire Mite

Phantom Train

How it works

1. Activate Phantom Train by sacrificing Haywire Mite.
2. When Haywire Mite dies, it and Mortuary triggers.
3. Resolve the Mortuary trigger, putting Haywire Mite from your graveyard onto the top of your library.
4. Resolve the Haywire Mite trigger, causing you to gain 2 life
5. Resolve the Phantom Train ability.
6. Cast Haywire Mite from the top of your library by paying 1 life due to Bolas's Citadel.
7. Repeat.

This ingenious engine uses Bolas's Citadel to turn your library into your hand, letting you cast Haywire Mite directly from the top for just 1 life instead of its mana cost. You then feed that same Haywire Mite to Phantom Train's sacrifice ability to animate the vehicle and pump it with a +1/+1 counter. As the insect dies, Mortuary immediately catches it, neatly placing Haywire Mite back on top of your library so Bolas's Citadel can see it again. Best of all, Haywire Mite's own death trigger counters the life paid to the Citadel by netting you 2 life each loop, keeping your life total safe while you spin the combo indefinitely.