Here is my general idea, to gauge how it would work out in this RP;
A member of the castle of Lithia's household guards; sworn to defend the royal family since the house of Lithia first came unto power. He/She is perhaps the sub-commander... but his/her ambitions are literally limitless. (I'll just use the feminine from now on...) She wants to be the commander of the household guard... for now. But like I said, limitless ambition- if there is an opportunity for her to influence the succession- she will exercise every wit and ounce of strength of hers' to ensure the results are to her favor. She always manages to be at the right... or wrong place at the right time.
She is a warrior by profession, but her self-preservation and ambition ensures she remains safe. She has no thrill for battle, but for victory. She is cunning and ruthless, using sex as her weapon as much as she would use forgery/deception/armed force.