Mortuary + Serrated Scorpion + Phantom Train + Gwenom, Remorseless

Mortuary

Serrated Scorpion

Phantom Train

Gwenom, Remorseless

How it works

1. Activate Phantom Train by sacrificing Serrated Scorpion.
2. When Serrated Scorpion dies, it and Mortuary triggers.
3. Resolve the Mortuary trigger, putting Serrated Scorpion from your graveyard onto the top of your library.
4. Resolve the Serrated Scorpion trigger, causing you to gain 2 life and dealing 2 damage to each opponent.
5. Resolve the Phantom Train ability.
6. Cast Serrated Scorpion from the top of your library by paying 1 life due to Gwenom.
7. Repeat.

This lethal loop is masterminded by Gwenom, Remorseless, whose ability lets you cast creature spells directly from the top of your library by paying life instead of mana. With Mortuary waiting in the wings to recycle every fallen creature straight back to the top of your library, you have an endless supply of ammunition. You feed that cycle by using Phantom Train's activated ability to sacrifice Serrated Scorpion, which triggers its own demise to drain your opponents of their life while also feeding Gwenom's life-payment requirement.