The Membrane of Sarkantha
the gluey film stretched over doorways
A semi-sentient, gluey film found stretched across cave entrances and doorways. Can be slashed with a blade but will spray you with acid: Test Agility DR14 or take d6 damage. Another option is to forcefully push yourself through it: Test Strength DR12 or become stuck. To escape, test Strength DR14. Fail and the DR to escape increases by +2 until it reaches 20. At this point you are screwed — you die and become one with the expanding membrane.
Often paired with Sarcopha-Ghost in the same source sheet — both dungeon hazards
Sarkantha itself is unnamed elsewhere — origin entity / land / spell unknown. Whether one membrane connects to another network is open. The fate of those who "become one with the expanding membrane" — added to a hive intelligence? Permanently dissolved? — is undefined.