Sharuum the Hegemon + Coretapper + Magistrate's Scepter + Baboon Spirit

Sharuum the Hegemon

Coretapper

Magistrate's Scepter

Baboon Spirit

How it works

1. Activate Coretapper's first ability by tapping it, putting a charge counter on Magistrate's Scepter.
2. Activate Coretapper's second ability by sacrificing it, putting two charge counters on Magistrate's Scepter.
3. Activate Magistrate's Scepter's second ability by tapping it and removing three charge counters from it, causing you to take an extra turn after this one.
4. Activate Baboon Spirit by paying 3, exiling Sharuum.
5. At the beginning of your end step, Baboon Spirit triggers, returning Sharuum from exile to the battlefield.
6. When Sharuum enters the battlefield, it triggers, returning Coretapper from your graveyard to the battlefield.
7. Repeat each turn.

This intricate engine achieves infinite turns by continuously resurrecting its key components, powered by Coretapper's ability to rapidly load Magistrate's Scepter with charge counters. While Coretapper sacrifices itself in the process, Sharuum the Hegemon steps in upon entering the battlefield to fish Coretapper right back out of the graveyard. To make this recursion repeatable every single turn, Baboon Spirit conveniently steps up to exile Sharuum and safely return it to the battlefield at the end step, resetting the entire loop anew.