Urza, Prince of Kroog + Metalworker + Retreat to Coralhelm + Darksteel Citadel

Urza, Prince of Kroog

Metalworker

Retreat to Coralhelm

Darksteel Citadel

How it works

1. Activate Metalworker by tapping it and revealing at least three artifact cards from your hand, adding at least six C.
2. Activate Urza by paying 6, creating a token copy of Darksteel Citadel that is a 1/1 Soldier.
3. When the Darksteel Citadel token enters the battlefield, Retreat to Coralhelm triggers, untapping Metalworker.
4. Repeat.
5. If you have four or more artifact cards in hand, this combo nets infinite colorless mana, and you may target any artifact you control to get infinite copies of them.

This loop relies on transforming ordinary land drops into an engine of explosive replication, fueled entirely by Metalworker's massive mana production when you have enough artifacts in hand. By funneling that colorless mana into Urza, Prince of Kroog's ability, you can churn out a steady stream of copies—using Darksteel Citadel as a cheap, indestructible target that triggers Retreat to Coralhelm each time it enters the battlefield. That landfall trigger immediately untaps Metalworker, allowing you to repeat the entire process to generate infinite colorless mana and an endless army of artifacts and creature tokens.