Frederick is a member of Chrestomanci's staff during Gabriel de Witt's time as Chrestomanci. He is, apparently, a spirit traveller like Mordechai Roberts, because Gabriel de Witt issues orders for him to prepare to go into another trance after he transports both Christopher and Flavian back to Chrestomanci Castle. Flavian had called for the Chrestomanci because Christopher burned himself up while trying to start a campfire.
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