An opponent controls an indestructible creature, or you have a way to give an opponent's creature indestructible.
You control a number of artifacts greater than two times the indestructible creature's toughness.
Steps
Give an opponent's creature indestructible, if needed.
Activate Ghirapur Aether Grid by tapping two artifacts you control, dealing 1 damage to an indestructible creature an opponent controls.
If the creature has less than 0 toughness, Magmatic Galleon's second ability triggers, creating a Food, a Clue and a Treasure artifact token.
Repeat from step 2.
Once you have infinite tokens, you may sacrifice them to their abilities, or tap them via Ghirapur's Aether Grid to deal infinite damage to any target(s).