The Glauxian Sister's Retreat is a place where owls get taken care of. One known owl who retreated to the Glauxian Sister's Retreat was Dewlap
The First Collier
In The First Collier, it is briefly mentioned that Queen Siv and Myrrthe disguise as gadfeathers and seek shelter from the Glauxian Sisters. One of the Glauxian Sisters was Rorkna, who was one of Siv's cousins. The Glauxian Sisters were all spellbound by the Nacht Ga'. Myrrthe suspected this and she returned to Siv. Later in the book, Grank also seeked shelter from the Glauxian Sisters. He resisted the Nachtmagen with his magic, and broke the spell which the Hagsfiend cast by driving an ice splinter into Rorkna's gizzard which caused her and the rest of the sisters who did not remember anything of that time to snap out of the Nacht Ga'. He did not tell the sisters the truth of the encounter with the Hagsfiends because it might lead them to doubt their beliefs.