The Fisher King appears in The Lady of the Lake. There he is the human lover of Nimue. When Condwiramurs Tilly first arrives at the lake, she is taken to Nimue's island by the Fisher King and he does not leave a particularly favourable impression on her, but during her stay, she grows to appreciate him. He is described as a short, stocky, compact man with a grizzly mop of hair as curly as a caracul lamb's. His face is swarthy and weather-beaten as tanned leather and his chin is pointy and covered with a scrabbly grey beard.
Nimue also specifically forbids Condwiramurs from "taking advantage" of the Fisher King.
In the Blood and Wine expansion
to be added
In The Witcher computer game
The Fisher King is a servant of the Lady of the Lake, who lives in a modest hut on the lakeshore outside Murky Waters. He also seems to be the postmaster for the village and handles the delivery of a letter from Geralt to his lover to Vizima.
He can usually be found in or near his hut. During the day, he either fishes (surprise!) or sits on his stool outside his hut contemplating whatever it is a Fisher King might contemplate. It is here that Geralt finds him to ask about borrowing his boat to get to Black Tern Island. His silent nature could make this a problem, but thankfully does not.
He is not a very talkative guy, and manages to communicate mostly with a series of Mhm's and Uhm's. Sometimes it is more like twenty questions than a conversation, but when push comes to shove, he can speak, he simply chooses not to, mostly.
There is some suggestion that he is more than just a servant of the Lady of the Lake. The hermit says that the Fisher King and the Lady of the Lake take care of Murky Waters. Additionally, the lady herself suggests that he was her lover, on at least one occasion. On this topic, if Geralt earns the Lady's most intimate reward, he can afterwards ask the question "Why the Fisher King?" which leads her to playfully belittle Geralt's sexual prowess by comparison.