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 Adalbert, 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.
Megascopes can also unleash some dangerous effects if they are tampered with or if something interfers with their initial function. Someone trying to use a megascope must be sure all megascope crystals are flawless or run the risk of being ripped apart. Dimeritium within the proximity of a megascope could cause a crystal to explode when in use since dimeritium can interfer magic.