Given to Morrolan e'Drien as a gift from his godess Verra, the window(s) in the tallest tower of Castle Black is a magical artifact that allows passage to many places, both on Dragaera, and off. The number of windows in Morrolan's tower seems to vary from moment to moment, and depending on who is doing the counting. The existence of this window is considered an Imperial secret, known only to a select few individuals. Considering the possibility of using these necromantic gates in reverse, it would be unwise to allow the Jenoine to learn of the window(s).