Ancient Den, Goblin Welder, Great Furnace, and Retreat to Coralhelm

Prerequisites

• Ancient Den in your graveyard
• Goblin Welder on the battlefield
• Great Furnace on the battlefield
• Retreat to Coralhelm on the battlefield
• Goblin Welder does not have summoning sickness

Steps

1. Activate Goblin Welder by tapping it, causing you to sacrifice Great Furnace and return Ancient Den from your graveyard to the battlefield
2. Ancient Den enters the battlefield, triggering Retreat to Coralhelm, untapping Goblin Welder
3. Activate Ancient Den by tapping it, adding
4. Activate Goblin Welder by tapping it, causing you to sacrifice Ancient Den and return Great Furnace from your graveyard to the battlefield
5. Great Furnace enters the battlefield, triggering Retreat to Coralhelm, untapping Goblin Welder
6. Activate Great Furnace by tapping it, adding
7. Repeat

Results

• Infinite landfall triggers
• Infinite red mana
• Infinite white mana