As this is an unusual premise, I need a bit more information than would usually be the case for your RtJ. Please include the following.
1. Character name
2. Character "race" i.e., familiar type
3. Any familiar archetypes that you are taking
4. Personality information
5. Backstory as relevant

And also include some information about your character's master. Note that this character is an NPC, but will be based on your description.
1. Name
2. Race and class (including how they have you as a familiar)
3. Personality
4. Relationship with you (are they friendly? Adversarial? Uncomfortably close? Abusive? Forgetful about your existence until they need something from you?)