Magmatic Galleon, and Mayhem Devil

Prerequisites

• Magmatic Galleon on the battlefield
• Mayhem Devil on the battlefield
• An opponent controls an indestructible creature, or you have a way to give an opponent's creature indestructible
• You control a number of Treasure tokens greater than the indestructible creature's toughness

Steps

1. Give an opponent's creature indestructible, if needed
2. Activate a Treasure token by sacrificing it, adding one mana of any color
3. Mayhem Devil triggers, dealing 1 damage to the indestructible creature
4. If the creature has less than 0 toughness, Magmatic Galleon's second ability triggers, creating a Treasure artifact token
5. Repeat from step 2

Results

• Infinite colored mana