The one after Witch's Hut, is 'Wurm', hope that helps! Once you find it, talk to Bingo on Resonarion.
Ahh! Thank you so much. I missed that one on my clean-up because it doesn't have a door icon on the map.
100% achieved! My OCD thanks you.
Did you 100% save file 4?
Not yet, working on it.
