Oly's Keep is a small keep in the Kosmosi Mountains within the territory and control of the Crimson Empire, near the border of the Lunar Collective and Night's End.

It was constructed in 3E090 by Oliver "Oly" Darkmere, one of the founders of the Blackreyne Brotherhood. The gnome retired from his duties at age 202 in 3E097, and turned Oly's Keep into a monastery for the rest of his days.

During the Great Aurian War, in 3E225 the monastery was taken over by the Crimson Army. The monks were told to relocate, and the keep was transformed into a prison. It remained a prison even after the war, usually being used to house Lunar prisoners caught at the border.