Crystal ball

From The Heretic Knowledge Vault

Standard fantasy magic-user paraphernalia, presumably used for scrying (seeing at a distance). According to Bani's flashback, crystal balls are status symbols among the girls at the Sashi Mu Academy of Thaumaturgy and Conjuration. Size matters: the smaller the crystal ball, the higher the status of the owner. (Bani, of course, resents this, as she resents just about everything else about most of her classmates.)

Neither Meji, Bani nor Sarine have ever been seen to use, or necessarily to own, a crystal ball. Sarine, at least, seems to have an uncanny ability to find interesting things (notably Jon Amraphel) at a distance, so perhaps she doesn't need one.