Appearance: Thanos wouldn't stand that much apart from an average Black Marches (or more precisely, Dragonportian) citizen if they Marches were … solely populated by xephs and perhaps quite sightly ones at that. Compared to the majority of its kind this xeph in particular has mostly greenish, as opposed to yellow-ish, eyes but other than that only his somewhat comely countenance would stand apart.
The man sports a quite traditional xeph hairstyle which simply boils down to a mostly shaved hair with only a single braid left hanging not unlike a ponytail. As far as the outfit is concerned it is similarly obviously indicating his distant, exotic origin due to its more than noticeable style and fabric type (which is a variant of a spidersilk in itself).
Personality: Thanos, due to his background, is much more open-minded (the irony, when considering that Zarthia is pretty much a psi-cracy) than an average lower-class citizen of the Principality of Zarthia, treating the outsiders with little to no suspicion of ill-will which is otherwise commonly attributed to those 'barbarians' as the kin of his simply denominates pretty much the entirety of the foreigners. Partway distant, partway aloof part contestantish part… overinquisitive - Thanos is more than fascinated by those distant lands in which he has found himself as a part of a mission from his order.
Background: Born roughly ~22 years ago to not the most affluent nor otherwise possessing any better kind of standing family of xephs Thanos' parents decided to sent him to a monastery, as he was the youngest child … the 7th one at that and the material circumstances would not allow them to grant him proper and dignified upbringing otherwise. In spite of being not particularly able to withstand the regimes of sustained concentration… he proved to be a natural talent, genius so to say which allowed him to master what otherwise took his peers years.
It didn't take long enough for Thanos to actually exceed some of his former masters and similar which brought the danger of, unintentionally, uprooting the already fragile standing of his within the organization.
In order to avert any chaos from ensuing Thanos was sent on a pilgrimage, a quest for knowledge and further mastery of the way he was taught - a pilgrimage leading him as far as to the lands of the south western hemisphere of the world of Arkus - towards Dragonport and the Marches.