Hell's Caretaker + Body Double + Shang-Chi, Master of Kung Fu

Hell's Caretaker

Body Double

Shang-Chi, Master of Kung Fu

How it works

1. During your upkeep, activate Hell's Caretaker by tapping and sacrificing it, returning Body Double from your graveyard to the battlefield as a copy of Hell's Caretaker.
2. Activate Body Double by tapping and sacrificing it, returning Hell's Caretaker from your graveyard to the battlefield.
3. Repeat.

This recursive loop relies on Hell's Caretaker trading creatures from the graveyard for those on the battlefield during your upkeep, but by having Body Double enter the graveyard and return as a copy of Hell's Caretaker, it takes over the exact same sacrifice-and-return duty. To make this engine function smoothly across turns without waiting for summoning sickness, Shang-Chi, Master of Kung Fu provides the crucial haste-like speed for activated abilities alongside a specialized mana pump that feeds right back into them. By cycling these two impersonators back and forth indefinitely, you generate an endless stream of death triggers, enters-the-battlefield effects, and sacrifice counts.