According to “The Witcher” books, the motivations of Emhyr (aka The White Flame on the Barrows of his Enemies) for wanting Ciri at Nilfgaard are nefarious and, frankly, abhorrent.
In Season 3 of the show, Ciri (Freya Allan) doesn’t know Emhyr (Bart Edwards) is her father, as she believes that Duny died alongside her mother when she lost both of her parents.
Based on cues from “The Witcher” books, we can speculate what will happen next. Emhyr plans to claim the throne by marrying and impregnating Ciri to fulfill Ithlinne’s prophecy.
In essence, marrying the Lion Cub of Cintra automatically legitimizes Emhyr’s rule beyond his coercive tactics, and Ciri’s child serves the purpose of thwarting the White Frost.
The video games depart from the incest storyline in the books, as they omit this unsavory aspect to paint Emhyr as a father who just wants Ciri to take over his rule.