The Shades of Magic trilogy closes with the balance among four parallel Londons pushed past its breaking point. An ancient enemy has crossed over from the ruin of Black London: Osaron, dark magic woken into will and voice, who takes hold of Red London and sets about claiming a crown of his own while decay spreads through the Maresh empire.
Kell Maresh, long believed the last surviving Antari, is pulled apart by competing loyalties — to the crown he serves, to Rhy, the prince whose life is bound to his own, and to a power he is no longer certain he controls. Delilah Bard, the Grey London thief who has survived every trial the last two books set her, must learn to master her magic before it bleeds her dry. The disgraced Captain Alucard Emery of the Night Spire gathers his crew for a voyage after something that should not be obtainable at all. And Holland Vosijk, the Antari of White London, finds himself in an uneasy alliance with the people who spent two books counting him an enemy.
Schwab's finale is a siege told from several sides at once — a trilogy about who is allowed to hold magic, and what holding it costs, arriving at its answer.