The Underworld Cookbook + Clock of Omens + Metalwork Colossus + Exalted Sunborn

The Underworld Cookbook

Clock of Omens

Metalwork Colossus

Exalted Sunborn

How it works

1. Activate The Underworld Cookbook's first ability by tapping it and discarding Metalwork Colossus, creating two Food tokens.
2. Activate Clock of Omens by tapping the Foods, untapping The Underworld Cookbook.
3. Activate Metalwork Colossus by sacrificing the Foods, returning it from your graveyard to your hand.
4. Repeat.

This crafty loop turns the humble artifacts you control into an infinite self-discard engine by exploiting a clever recycling loop. You start by using The Underworld Cookbook to discard Metalwork Colossus and churn out Food tokens, a process doubled entirely thanks to Exalted Sunborn's replacement effect. Once those tokens hit the board, Clock of Omens taps them to untap The Underworld Cookbook, while those same Food tokens are promptly sacrificed to pay for Metalwork Colossus's ability to return itself right back to your hand.