Mortuary + Bolas's Citadel + Kobolds of Kher Keep + Phantom Train

Mortuary

Bolas's Citadel

Kobolds of Kher Keep

Phantom Train

How it works

1. Activate Phantom Train by sacrificing Kobolds of Kher Keep
2. When Kobolds of Kher Keep dies, Mortuary triggers, putting Kobolds of Kher Keep from your graveyard onto the top of your library.
3. Resolve the Phantom Train ability.
4. Cast Kobolds of Kher Keep from the top of your library by paying 0 life.
5. Repeat.

This loop turns your library into a self-sustaining engine by exploiting the free mana cost of Kobolds of Kher Keep. With Bolas's Citadel allowing you to play cards directly from the top of your library and paying zero life for the free creature, you can continually feed Phantom Train's sacrifice ability. Each time the Kobolds hit the graveyard, Mortuary neatly intercepts them to place the card right back on top of your library, ready to be recast instantly.