Tales from the Inner Sea
The Shadow Cloth
3 foot by 3 foot square of night black velvet like material.
This cloth of unusual substance can be used to create a casting of Darkwall as the spell, with no time limit nor need to expend magic points to use. One simply casts it into the air and the cloth becomes the Darkwall. In all other ways it functions as the spell, though it cannot be dispelled. Only the owner (who to become its owner must perform an hour long attunement ritual expending 1 magic point in the process) can activate and deactivate it.
This cloth may have a very interesting backstory, but it will take formidable delving and investigative spells to probe it’s past, who created it and when.