While busting up some cultist activity, you encountered a gaping black rift in reality. The cultists were performing some sort of ritual on the rift that was bringing forth horrible nightmarish forms of teeth and claws into this reality. With the cultists and their minions dead, it seems the dark rift is now dormant. It is no less disconcerting, however. You briefly wondered whether you could enter the rift yourself, but finding some way to close the rift is probably the more prudent decision. There is an Aesther enchanter in Gloomhaven who may know more about this inter-planar stuff. She’s been known to ask for impossible favors before she helps anyone, though.
You have met the Aesther enchantress, Hail, at the Crooked Bone. Although a bit eccentric, she does seem quite capable. You have earned her favor by aiding in her endeavors. Perhaps now she can help you find a way to close the rift?
Hail required an elemental censer from a long dead elementalist's crypt. Unfortunately, the cultists inhabiting the crypt weren't keen on parting with it. You escorted Hail through the crypt until she could secure the censer, which she used to promptly dispatch the remaining undead. She's now ready to deal with the rift.
Throughout an elaborate ritual, you and Hail are assailed by demons unhappy with your intent to close the rift between your worlds. However once the ritual is completed, all the demons are sucked back into the rift, and the tear shrinks to a brilliant point, then disappears. As a bonus, you seemed to have helped Hail out with her research on enhancements considerably.