I asked this on yahoo but people were giving me bs like he isn't in the BoS when you clearly can be; I know this because you are asked to join the Lyons' Pride at the end of the main game and Owen Lyons says your apart of them. I'm just wandering because I like them and in the wiki it said all the Lyons' Pride members were Knight Captains.

You get the glorious Rank of Errand boy

It was never said what Rank the LW got so take your pick of what rank you want your character to have.