Magic is a core element of The Witcher franchise, and when it was revealed in Season 2 of the Netflix series that Yennefer lost her power during the Battle of Sodden Hill, it was a devastating blow as fans wondered if she'd lost her magic forever. For a sorceress like Yennefer of Vengerberg, magic empowered her in ways she couldn't have imagined even before Tissaia de Vries brought her to Aretuza. Her magic was chaotic, however, and fueled by an overwhelming amount of emotion that Tissaia encouraged her to set aside. When she finally came into her power, Yennefer was nigh unstoppable.
Source：https://www.cbr.com/the-witcher-why-yennefer-lost-powers/
