Keeper of the village archives on his planet. He was well-versed in the knowledge of Morgan Le Fay and the quest she established on his world -- a quest to weed out those unworthy of seeking Merlin's weapon, the Sangraal. His knowledge of her partially stemmed from the Parchment of Virtues, which he kept hidden in the archives.
Prior to the arrival of an Ori army Adria took his place, projecting a false image of Osric over herself in order to impersonate him. She used this deception to gain the trust of SG-1 when the team arrived, in the hopes that she would tag along on their quest until the time was right to take the Sangraal for herself.
While posing as Osric Adria made two crucial mistakes. She paraphrased a passage from the Book of Origin ("Truth eludes he who does not seek it with both eyes wide"). And she carried an Ori ring, which she used as "Osric's" item to give away and free the group from one of Merlin's traps. Both of these convinced Daniel Jackson that Osric was false. Adria revealed her true identity at the base of a mountain containing the Sangraal.
Osric may have never been a real person to begin with. However, if he hadn't been, then at least one villager was complicit in concealing the true nature of Adria. It is far more likely that Adria did away with him and created a projection of him for her own purposes.
The Quest, Part 1 - Following the burning of the Parchment of Virtues, "Osric" offers to lead SG-1 on their quest for the Sangraal.