From Guild Wars 2 Wiki
Flattened Ooze is a trophy required for the The Juggernaut III: The Colossus legendary weapon collection.“
— In-game description
- During the last fight of the Molten Furnace Fractal coat yourself with Mystic Chromatic Ooze and stand directly underneath a Stomper (the weapons test causing shockwaves) to be flattened.
- This item does not enter your inventory. It is added directly to the collection.