Look high for the way back
After collecting a key in the Underground Depths worms-and-acid area, look for a return route high near the ceiling. Keep your attention on the upper part of the cavern rather than only the acid-level path.
The nearby Life Node is optional. Leave it for later while you work on returning with the key, so the collectible detour does not distract you from the exit route.
Match the hint to your location
This hint concerns the return through the worms-and-acid cavern after obtaining a key. For the search that leads to the Undermoors passkeys, use the two branch entrances.