Mortal Instruments 06. City of Heavenly Fire

The Shadowhunters rally to defeat Sebastian once and for all in the spellbinding, seductive sixth and final book in the New York Times and internationally bestselling Mortal Instruments series. City of Fallen Heavenly Fire is a Shadowhunters novel.
Darkness has descended on the Shadowhunter world. Chaos and destruction overwhelm the Nephilim as Clary, Jace, Simon, and their friends band together to 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 of nightmare, tearing apart families and lovers as the ranks of his Endarkened army swell.
Nothing in this world can defeat Sebastian—but if they journey to the realm of demons, they just might have a chance… Lives will be lost, love sacrificed, and the whole world will change. Who will survive?