Kylie was illegally trained
Gunmages are described as being weaker than other mages, which is why they cannot use repeaters. Nothing stops a stronger mage learning their powers, but this would upset the delicate balance of power between other mage factions. Kylie was too strong to become a gunmage, but someone hid that fact.
Sierra was NOT Reassigned to Antarctica
Sierra's introduction is portrayed as an excuse to get rid of her. She is, however, highly competent and both fanatically loyal to, and in love with, Ravenna. Ravenna herself is a lesbian and, notably, the decision to send Sierra was made overnight. It's likely that Sierra is acting as Ravenna's agent in Gwen's operation and was sent because Ravenna trusted her, not because of her abrasive personality.
- If nothing else it has been confirmed that She and Ravenna are lovers and she's hiding the real reason she was sent.
