Maybe a hedge knight?
...I don't know what that means.
Historically, in a very general way, knights are bonded servants to the crown or lord upon whom they serve (which explains the core basis of loyalty and honor). Hedge knights however are free knights, generally anyone legitimately dubbed a knight, however lacking a master.
So you could either model it around that, or model your idea of a knight following a non-tangible or possibly-fictitious master :O Like natural forces, etc.
Edit because HISTORICAL ITCH:
Hedge Knight, in the general context, is more of a dubious term which may carry a negative context. In comparison, the probably-more-known term of knight errant; a knight on a mission, trying to prove him/herself or in search of completing some quest, but they often had a master or lord that they served. Hedge knights served no one but themselves and went about in search of money. (because if you strip away the romanticism surrounding the knights, you'll be facing the real situation of finance crises, and WHY having a master back in the feudal days helped a lot) They were little better than mercenaries and were often much more like bandits than anything else, or so goes the idea: Being a knight errant was an honor, while being termed a hedge knight was considered an insult. "Hedge" would pertain to the symbolism or idea :O as in contrast to the peasantry who had homes (or huts), the knight had none.
It's similar to the Japanese 'Ronin'.
However the Hedge Knight is probably popularized nowadays thanks to G.R.R. Martin's books and stoof :O
Coincidentally, my Myrmidon is modeled under the theme of a ronin.
Which I guess could actually even be better than if I had an introduction
;~; All those mugs I am familiar with! It's like only yesterday I saw them all in action.
I...don't think I'll be submitting a sheet in time considering that I've only until Saturday to keep trading thesis drafts for THE BIG DEFENSE in a week or two. (Sorry SC u~u, I deeply appreciate your PMs in checking up on me dough!)
If the delay gets to be too bad we might just have to all agree on a continuity break or something, where your character simply appears from thin air and is treated as if they were there all along.