Ob Nixilis, Captive Kingpin + Mortuary + Footlight Fiend + Phyrexian Altar

Ob Nixilis, Captive Kingpin

Mortuary

Footlight Fiend

Phyrexian Altar

How it works

1. Activate Phyrexian Altar by sacrificing Footlight Fiend, adding B/R.
2. When Footlight Fiend dies, it and Mortuary trigger.
3. Resolve the Mortuary trigger, putting Footlight Fiend on top of your library from your graveyard.
4. Resolve the Footlight Fiend trigger, dealing 1 damage to an opponent.
5. Ob Nixilis triggers, putting a +1/+1 counter on itself, and exiling Footlight Fiend from the top of your library with the ability to play it until your end step.
6. Cast Footlight Fiend from exile by paying B/R.
7. Repeat.

This delightful loop turns the humble Footlight Fiend into an infinite engine of doom by feeding it directly into Phyrexian Altar for mana. Every time the Fiend is sacrificed, Mortuary instantly catches it on its way to the graveyard and slides it right back onto the top of your library. Meanwhile, the Fiend's own death trigger pings an opponent for exactly 1 life, which joyfully wakes up Ob Nixilis, Captive Kingpin to grow larger, exile that very same Fiend off the top of your library, and grant you permission to recast it using the mana you just generated.