A megascope is a device used for many magical operations including communication and teleportation. It seems to aid or enhance a sorcerer's magical abilities and resembles the "Magic Mirrors" of The Witcher in function.
Aep Dearhenna created a prototype megascope that allowed the user to remotely view someone they had a close personal connection to. Cynthia and Adelbert, Nilfgaardian agents, were interested in this for its obvious spying applications. Depending on Geralt's choices in The Secrets of Loc Muinne it is either taken by them or used until it loses power becoming useless. It takes the form of a golden box.