Cassandra is a gryphon in that awkward state between young and adult, not quite belonging in either world and without much help guiding her through the transition. She tends to drift around with others in the same situation, being delinquent.
Cassandra and her father Hector moved to Cloudsville from Griffonstone after a fire destroyed their home, killing her mother and elder sister. Left largely on her own by a parent who is mostly only interested in his work, she has taken to drifting around and causing trouble. Although she has tried, she doesn't really feel that she fits in with the ponies, and mostly sticks to what few gryphons her age she can find.