Mortuary + Crimson Kobolds + Phantom Train + Gwenom, Remorseless

Mortuary

Crimson Kobolds

Phantom Train

Gwenom, Remorseless

How it works

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

This clever loop hinges on Gwenom, Remorseless, whose attack trigger allows you to play cards directly from the top of your library while paying life instead of their mana costs. Because Crimson Kobolds costs zero mana, you can recast it for free off the top of your library every time Mortuary automatically recycles it back to the top of your deck whenever it dies. To trigger that death, you feed the creature to Phantom Train's activation cost, which also pumps up the Vehicle with permanent +1/+1 counters.