Urza, Prince of Kroog + Metalworker + Retreat to Coralhelm + Ancient Den

Urza, Prince of Kroog
Metalworker
Retreat to Coralhelm
Ancient Den

Requires
All permanents on the battlefield. You have at least three artifact cards in hand. Metalworker does not have summoning sickness.
Steps
  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 Ancient Den that is a 1/1 Soldier
  3. When the Ancient Den 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
Results
Infinite creature tokens. Infinite copies of each artifact you control. Infinite colorless mana. Infinite ETB. Infinite landfall triggers.