The Witcher Characters: Books Vs. Games Vs. Netflix Show
3. Cahir
Cahir's only appearance in the games is also only in the form of a Gwent card. The depiction of him on the card is from after his time in the Nilfgaardian military, while the series' is at the prime of his service - explaining the different outfits.
There is also a Gwent card of Cahir in his Nilfgaardian armour, but that pretty much matches Sapkowski's description of the character: a faceless "rider", "his eyes gleaming through the slit in his huge helmet, framed by a bird of prey's wings". This is a recurring image that Ciri has nightmares about for some time.
Netflix didn't exactly take the usual approach to fantasy armour with the Nilgaardians, though that probably should not have been at the cost of the helmet's wings - given how key an image they were in the books.