City of Heavenly Fire recap

Jonathan Morgenstern's Endarkened destroy Institutes across the world, and the Clave withdraws every surviving Shadowhunter to Alicante while Jace struggles to control the heavenly fire burning inside him. Among the refugees are Emma Carstairs and the Blackthorn children of Los Angeles. Jonathan takes hostages, the fair folk are exposed as his allies, and he offers terms that amount to a demand for his sister. Clary, Jace, Simon, Isabelle and Alec let themselves be taken to reach him, and cross into Edom, a dead demon world ruled by Magnus's father Asmodeus. There Jonathan is struck with heavenly fire and Clary's family blade, which burns the demon blood out of him; for a few minutes he is the ordinary boy he might have been, and then he dies. The Endarkened are destroyed with him. To open the way home Asmodeus takes his price from Simon, stripping away his immortality and every memory of the Shadow World and returning him to Brooklyn as a human who knows none of them. The Clave imposes a punitive Cold Peace on the faeries, and Simon, at the very end, begins to remember.

Clary Fray is the daughter of Valentine Morgenstern, who twice tried to overthrow the Clave and purge the Downworlder races and was destroyed by the angel Raziel. Her brother Jonathan was given demon blood before birth; he posed as a Shadowhunter called Sebastian, killed the youngest Lightwood child, betrayed Alicante to demons and was killed in the war, then raised from the dead by the demon Lilith. Jace, who is a Herondale rather than a Morgenstern and was given angel blood by Valentine, was bound to Jonathan by Lilith's ritual so that neither could be killed without the other, and spent months under Jonathan's influence while Clary infiltrated their household. Clary's friend Simon, a vampire who can walk in daylight, summoned Raziel and traded away the Mark of Cain for the sword Glorious; Clary used its heavenly fire to sever the bond and free Jace, and the fire remained inside him. Jonathan escaped, took an infernal cup made from Lilith's remains to an old sacred site, and forced a company of captured Shadowhunters to drink, turning them into the Endarkened: fighters who keep their training and lose themselves entirely. Luke's sister Amatis is among them. Magnus Bane ended his relationship with Alec Lightwood after learning Alec had been asking an old vampire how a warlock might be made mortal. Jonathan now commands an army the Clave has never faced.

Jonathan's Endarkened begin destroying Institutes one by one, striking without warning and leaving few survivors. Los Angeles falls: the Blackthorn children lose their father and their home, and Emma Carstairs, twelve years old and close to Julian Blackthorn, loses her parents and survives the attack with him. The Praetor Lupus, the werewolf order that guards the newly turned, is also attacked, and Jordan Kyle is killed there. The Clave orders every Institute abandoned and every Shadowhunter withdrawn to Alicante, which fills with frightened and grieving refugees. Jace, meanwhile, cannot control the heavenly fire in him: it answers to his temper, burns what he touches, and makes him the one weapon the Endarkened have no defence against and the one person nobody can stand next to.

In Alicante the Consul, Jia Penhallow, tries to run a war with a Council that would rather argue about Downworlders. Brother Zachariah works with Jace on containing the fire. Jocelyn gives Clary a Morgenstern blade she has kept hidden for years, one of a pair, and tells her what it was made for and who carries its twin. Emma and Julian are among the survivors quartered in the city, and Emma will not accept the Clave's account of how her parents died. Simon and Isabelle are together openly, which the Clave dislikes; Alec cannot get Magnus to talk to him. Then Jonathan makes contact and sets out his terms, and they are not about territory: he wants his sister.

Jonathan takes hostages to force the Clave to listen, and it emerges that the fair folk have been supplying and sheltering him. The Council's response is punitive and immediate, and the alliance the last war built starts to come apart. The Endarkened cannot be reasoned with, cannot be turned back, and grow in number every time an Institute falls. Magnus is drawn further in as it becomes clear where Jonathan's power is being drawn from, and what he knows about that realm has to do with a father he has never named. Attempts to hold ground fail, and the Clave is reduced to defending one city.

Jonathan proposes a parley and names his price for sparing the Nephilim: Clary, delivered to him. Rather than let the Clave decide, Clary, Jace, Simon, Isabelle and Alec agree among themselves to be taken, since being taken is the only way to reach him at all. Magnus goes with them because none of the rest can survive where they are going. What passes for Jonathan's stronghold is not on this world: he has been operating out of Edom, a realm burned to ash long ago by demons and ruled by one of the Princes of Hell. They cross over, and the way back closes behind them.

Edom is a dead world of ash and heat under a wrong sky, with the ruins of a city that mirrors Alicante. The group is separated and hunted; Magnus is taken by the realm's ruler, who turns out to be Asmodeus, a Prince of Hell and Magnus's father. Jonathan holds his court in the ruins with the Endarkened around him, and makes Clary an offer that has been the point of everything he has done: he intends to unmake the world he was born into and rule what replaces it, with her beside him. Jace's heavenly fire, uncontrollable everywhere else, is the one thing in Edom that Jonathan's people cannot stand against.

The confrontation goes as far as it can go. Jonathan is struck with heavenly fire and with the Morgenstern blade Jocelyn gave Clary, and what burns out of him is the demon blood Valentine put in him before he was born. What is left for a few minutes is the boy he would otherwise have been: frightened, unremarkable, aware of what has been done in his name and of what he has done. He dies as that boy, with his mother and his sister there. His army cannot be restored and the war ends with the Endarkened destroyed. The Shadowhunters have won, and are stranded in a dead world with no way home.

Asmodeus will open the way out of Edom, and he sets his own terms. The price is paid by Simon: his vampirism, his immortality, and every memory of the Shadow World and everyone in it. The others return to Alicante; Simon wakes in Brooklyn as an ordinary human who has never heard of Shadowhunters, does not know why he has been away, and does not recognise Clary or Isabelle when they come to find him. Magnus, who understands what his father took, has nothing to say about it that helps.

In the aftermath the Clave imposes the Cold Peace on the fair folk for their part in the war, stripping them of their Council seat and their protections, and it falls on Nephilim with faerie blood as well; the Blackthorns lose their eldest sister to it. Emma Carstairs and Julian Blackthorn are sent back to Los Angeles and bind themselves as parabatai. Brother Zachariah is burned free of what made him a Silent Brother by the heavenly fire and returns to mortal life and to the woman who waited a very long time for him. Magnus and Alec repair what Alec broke, Jocelyn and Luke marry, Maia takes over the New York pack, and Jace, no longer carrying the fire, has an ordinary life to try. Simon, still without his memories, is taken in hand by people who refuse to let him go, begins the process of Ascension to become a Shadowhunter, and starts to remember.

The confrontation happens in Edom, the burnt demon world Jonathan has been drawing on. Jace's heavenly fire and Clary's Morgenstern blade are used together, and what they burn out of Jonathan is the demon blood Valentine gave him before he was born. For a few minutes what remains is the boy he would otherwise have been, frightened and ordinary, and he dies as that boy, in front of the mother and sister who had given up on him. His army of Endarkened cannot be restored and the war ends with them destroyed. Getting home costs more than the fighting did: Magnus's father Asmodeus, who rules Edom, sets his own price for opening the way, and Simon pays it, giving up his vampirism, his immortality and every memory of the Shadow World. He is returned to Brooklyn as an ordinary human who does not recognise any of the people he saved. Afterwards the Clave imposes the Cold Peace on the fair folk for their part in the war, which punishes those with faerie blood among the Nephilim as well. Brother Zachariah is restored to mortal life by the heavenly fire and reunited with the woman who waited for him; Magnus and Alec repair what Alec broke; Jocelyn and Luke marry; Emma Carstairs and Julian Blackthorn go back to Los Angeles bound as parabatai. In the closing pages Simon begins Ascension, and his memories start to come back.