"Do you really wish to know?" — Spoilers from the books and/or adaptations to follow!
Oswin was the stablemaster at Crow's Perch.
Biography[]
In May 1272, the fortresses' barn was struck by lightning and set ablaze, and Oswin became trapped in the stables.
If Geralt chose to save him: The witcher Geralt of Rivia climbed through the roof down into the stables and opened the barred door to rescue him from the fire. He later showed his gratitude by offering a monetary reward to Geralt the next time the witcher visited Crow's Perch.