Silvia Moreno-Garcia’s 2021 The Return of the Sorceress is a standalone secondary-universe fantasy novella.
Yalxi, Supreme Mistress of the Guild of Sorcerers, has been deposed. But her usurper Xellah has made a fatal error: he has kept her alive as a prisoner so that he can make use of her magic-imbued blood. Dead foes may not be useful as sources of magic but living foes can escape, which is what Yalxi has done.
Wounded and stripped of the Diamond Heart from which so much of her power came, Yalxi is nevertheless an opponent of whom Xellah should be wary.