Mirror of Nehaleni

From Witcher Wiki

Nehaleni's Mirror is a magical artifact with oracular abilities.

Aridea, stepmother of Renfri and Fredefalk's second wife, owned such a mirror.

[edit] In The Witcher computer game

In Act IV, Alina, a girl from the village of Murky Waters, is said to have owned such a mirror, but it is broken. It is not clear if she broke it herself or if it was always broken. If she did break it, then why she did so, no one knows, but finding the shards and mending the mirror is part of a quest that's required to finish the game.

Geralt describes these mirrors as coming in only two varieties: polite and broken.