Mortuary + Bolas's Citadel + Moonlit Wake + Myr Scrapling

Mortuary

Bolas's Citadel

Moonlit Wake

Myr Scrapling

How it works

1. Activate Myr Scrapling by sacrificing it.
2. When Myr Scrapling dies, Mortuary and Moonlit Wake trigger.
3. Resolve the Mortuary trigger, putting Myr Scrapling from your graveyard onto the top of your library.
4. Resolve the Moonlit Wake trigger, causing you to gain 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 cunning loop uses Bolas's Citadel to cast Myr Scrapling directly from the top of your library while bypassing its mana cost with life payments, which Moonlit Wake neatly offsets by healing you every time the creature perishes. Whenever you sacrifice Myr Scrapling to fuel its own ability and place a +1/+1 counter, Mortuary catches it on its way to the graveyard and immediately tucks it right back onto the top of your library. Because Bolas's Citadel lets you perpetually gaze at and play from that top spot, the cycle feeds itself indefinitely, netting you an endless stream of artifact sacrifices, death triggers, and lifegain.