Nightmare Crag

 is a location that appears in Stormhaven south east of Koeglin Village. It is a place of worhip and sacrifice for the Supernal Dreamers Cult. On the way up to the top is a tower with another offering table.

Rozenn's Dream
The Supernal Dreamers also took Ingride's daughter, Rozenn Vanne, and they're apparently planning a similar ritual using her as the vessel for some daedric spirit. The Vestige promised Ingride they would stop them.