Cahir Mawr Dyffryn aep Ceallach, or simply Cahir, was from Vicovaro. He was the son Ceallach and Mawr, the brother of Dheran, Aillil. He was also a Nilfgaardian Intelligence officer who first appeared in Blood of Elves, though he is not named in that novel. It only becomes clear in later novels that he is the black knight with the bird of prey wings on his helmet who invades Ciri's dreams.
When we first meet Cahir, he has recently been released from two years in prison from which he had only expected to escape via the gallows. The emperor decides to give him one more chance, adding that if he doesn't succeed, the executioner's axe still awaits him. He also states that the chance of a pardon is extremely small and that of forgiveness, non-existent. All this relates to a mysterious incident two years earlier, but no further details are provided. Emhyr var Emreis, the emperor of Nilfgaard tasks him with finding Ciri.
Later, he joined Geralt's party but not easily. Geralt nearly killed him on at least three occasions before finally grudgingly accepting him into his party. The first time was during the coup on Thanedd Island, then again later while Cahir was being transported as a prisoner in a coffin by hawkers.
He loved Ciri. He confessed this to Geralt shortly before he died at the hands of Leo Bonhart in the assault on Stygga. He told Bonhart that he was the witcher but the seasoned killer was not frightened by this bluff and defeated the "Black Knight" in very few moves. Though he seemed an enemy at the outset, his sacrifice gave Ciri and Angoulême time to escape.
- Cahir had stated that apart from two brothers he also had three sisters - although nothing more apart from their existence has been explained.
- Cahir was unable to fully bend three fingers of his hand which had been cut by Ciri in a sword duel during the Thanedd coup.
- Dandelion was fond of making fun of his (and Regis's) long name(s).
- Cahir was very often called "Nilfgaardian" by various people, he was always correcting them, stating that he was from Vicovaro.
- Cahir was Assire var Anahid's cousin.
- The Armor of Vicovaro's name in the def_shops game assets file is called "Cahir Armor", a reference to the fact he was from Vicovaro.