TJByrum: 
I'm okay with the foreign country character, but other than being a mercenary I see no real way for them to relate to the story so I'm going to scrutinize your character story.

Caste would be the persons standing in terms of affluence. You have serfs who are essentially slaves, freemen who own their own land, lords who own a lot, aristocracy which are the rich essentially, then nobles right up to the king himself. There would also be outlaws or criminals. Essentially a serf would have no sway over a noble and is unlikely to have any weapon other than something makeshift. A noble might have a full suite of armour, a horse and even others riding together with them. 

Auxiliary is anything unmentioned that may be good to know about. Such as if you have a seax keeping with the character motif.