Witcher Fun Facts from the Table-Top Role-playing Game
These facts are about as canon as the lore in the game or in the reward trees for the gwent app as it is put out by CDPR. These are the things that stuck out to me the most, there are obviously more facts than these in the TTRPG.
• There is a sentient species living north of Kovir & Poviss despite it being widely believed that habitation farther north is impossible. The only way people on the Continent know this species exists is because some of their art will occasionally show up in Kovir & Poviss. It is not known whether those living there are human or something else. (If I was in charge of the TTRPG, the species living up there would be orcs because according to the wiki, Elder Speech was developed by Sapkowski for use by elves and orcs. Obviously orcs never showed up in the series but having them live up there would be a nice Easter egg.)
• The man that decapitates Yennefer's horse at the beginning of Witcher 3 is from Gemmera, a vassal of Nilfgaard and the sword he is weilding is called a torrwr
• It is implied that Cat witchers sleep four to a bed while they are at the cat caravan as the wagon type they use has an interior that is described as having one large bed and one small piece of furniture (a wardrobe, dresser, table, etc.) but can comfortably sleep four.
• Prosthetics designed specifically for witcher and sorceress use exist
• No ship from the Continent has ever returned from Ofier (which is located past Skellige for whatever reason I thought it was east of Zerrikania but I think that's because I'm a dumbass looking back) though whether that is "because they perished or because they prefer Ofier is not known."
• It's implied there are witchers in Ofier, which means that either Ofieri mages had the same idea as mages from the Continent or that witchers from the Continent traveled to Ofier (if I was in charge, the Ofieri witchers would be the Crane witchers from that non-Sapkowski short story collection)
• Mutagens were applied to women by the Manticore witchers but whether it worked or not is "inconclusive." Note that the TTRPG book is written from the POV of a Temerian dwarf and a scholar from Oxenfurt so weather or not these mutagens took is genuinely up in the air.
• Memories of one's life before being taken by a witcher directly affect how likely a trainee is to survive the mutation process. If you do not have memories before your life at whatever witcher headquarters, you are more likely to die during mutations.
• Geralt is not the first witcher to be famous and have ballads sung about him. There was a Griffin witcher called Raven who had a similar level of fame.