Mango
The Mango is inside the Mango Sanctuary; the Wormfish Exchange sends you there after you confirm an offering of one Mether's Flesh, which is consumed.
Layers this guide uses
The route to the Mango starts at the Wormfish Exchange on the overworld map. The exchange sends you into the separate Mango Sanctuary, where the Mango is found.
Where is the Mango entrance?
Open the Wormfish Exchange on the interactive map. It is west of Marrow Keep, in the same broad part of Fainweald as the Special Moonshine pickup.
This exchange is the entrance to the Mango Sanctuary. Its offering requires one Mether’s Flesh before opening the route inside.
What should you bring?
Bring one Mether’s Flesh. The offering consumes it when you confirm the trade. There is no Mether’s Flesh pickup on the current map, so obtain one before making the trip.
At the exchange, use the offering interaction and follow the prompt that opens the sanctuary route.
Why the Mango itself is not pinned
The world map can take you as far as the Wormfish Exchange. After it sends you into the sanctuary, there is no interior map to guide the remaining steps.