Ciri will be the second playable character in the game, with her own skill set and abilities.
When the 'Elder Blood' trailer was shown during The Game Awards just over a week ago, just before it was revealed the devs announced a second playable character would be included in the game, but they never specifically said who that would be. Well, now CD Projekt RED have cleared everything up, and reveal that it's Ciri.
Ciri is the white-haired lady in the trailer, by the way. She is described as "a descendant in a long-lost Elven-blood lineage" and "plays an important role in the Witcher lore," say the devs. Ciri is a "powerful, living weapon capable of both healing and destroying the world she inhabits."
Geralt is searching for her as she is on the run from the Wild Hunt, and whilst she is the second playable character in the game it's worth noting that she won't have as big a playable role as Geralt. "While Ciri is a major character, she is not a playable character in the same way as Geralt - the game is still about him, his story and how you, as the player, choose to face the choices and encounters in front of you," CD Projekt RED clarified.
Ciri's abilities include being able to teleport, and possessing sword skills, and you will be able to unlock further skills as you progress with her.