Mortuary + Bolas's Citadel + Myr Scrapling + Susurian Voidborn

Mortuary

Bolas's Citadel

Myr Scrapling

Susurian Voidborn

How it works

1. Activate Myr Scrapling by sacrificing it.
2. When Myr Scrapling dies, Mortuary and Susurian Voidborn trigger.
3. Resolve the Mortuary trigger, putting Myr Scrapling from your graveyard onto the top of your library.
4. Resolve the Susurian Voidborn trigger, causing you to gain 1 life and target opponent to lose 1 life.
5. Resolve the Myr Scrapling ability.
6. Cast Myr Scrapling from the top of your library by paying 1 life.
7. Repeat.

This elegant engine turns a humble automaton into an endless loop by uniting life manipulation with library control. Through Bolas's Citadel, you bypass traditional mana costs entirely, casting spells straight off the top of your library for a small pittance of life while Susurian Voidborn cushions that cost by draining your opponents and padding your life total with every single death. To keep the gears turning, Myr Scrapling sacrifices itself to distribute a +1/+1 counter, instantly triggering Mortuary to slip the robot right back onto the top of your library, primed to be cast all over again.