Excalibur Reigning — Kathryn Rose

It all ends in a grand, sweeping, soaring finale -- Vivienne has lost all she holds dear, and the only way to fix things is to steal a dark spell as Merlin urges her on, one that could finally set everything right. But thievery of such dark magic might come at the cost of Vivienne's very existence. Camelot's quest to claim the Holy Grail before the monstrous Black Knight will only grow more desperate from there. A battle in the skies has erupted above Jerusalem, a violent clashing of Spanish rogues, Irish Druids, and Azur's warriors all seeking the mystical chalice. The clocks are ticking, the Black Knight's aeroship is unstoppable as it soars toward Avalon, and Vivienne risks becoming the next Morgan le Fay if she can't beat the monster there first.