In this dazzling and long-awaited conclusion to the acclaimed Mortal Instruments series, Clary and her friends fight the greatest evil they have ever faced: Clary's own brother.
Sebastian Morgenstern is on the move, systematically turning Shadowhunter against Shadowhunter. Bearing the Infernal Cup, he transforms Shadowhunters into creatures out of nightmare, tearing apart families and lovers as the ranks of his Endarkened army swell.
The embattled Shadowhunters withdraw to Idris - but not even the famed demon towers of Alicante can keep Sebastian at bay. And with the Nephilim trapped in Idris, who will guard the world against demons?