His true identity is Robin Hood, the chivalrous thief. However, this Robin Hood is merely one of the many "Robin Hoods". This particular incarnation was originally the child of a wandering Druid, an orphan who lost his father when very young. He received knowledge of the forest from his Druid father, was proficient at survival in the forest, and also was friends with the forest fairies that the villagers could not see. For this reason, the villagers treated him as an outcast, believing him to be possessed by fairies. The villagers did not accept an orphan like him and he too did not compromise with the villagers. But, even still, it seems that he felt an obligation in taking care of his father at his last moments. He lived as the black sheep of the village, a young man without relatives who lived in the village's outskirts located near the spot where his parents had died In Fate/Extra

Spoiler

He is Dan Blackmore's Servant. He is somewhat virtuous and a little cowardly. In order to conceal his immature self who fusses over justice, he puts up a frivolous attitude. Values life over death and seems to believe that something warm should remain at the end of surviving. But then again, all these are things that he never obtained, so he can only but shrug his shoulders while saying "such things are like empty dreams".

(Source: Type-Moon Wiki)