Belly of the beast Trophy in Yoku's Island Express
Belly of the beast
Discover Fosfor’s Lair
How to unlock Belly of the beast
Fosfor's Lair is located underground, pretty much immediately below the starting location - you'll see it on the map included for WickerKing above. You'll need the Divefish upgrade before you can actually reach this area, but once you arrive here, you should then earn the trophy.