In the fifth book of the Mortal Instruments series, titled "City of Lost Souls", the following events occur:
1. Return to Idris: The story begins with Clary and her friends returning to the Shadowhunter capital, Idris, after the events of the previous book. Clary is reunited with her family, including her father Robert and brother Max.
2. Tensions escalate: Tensions are high in the Shadowhunter world as the conflict between the Dark Council and the Clave intensifies. Clary and her friends find themselves caught in the middle of this conflict, facing new threats and challenges.
3. The Soul-Sword: Clary discovers that she has a unique connection to a powerful weapon known as the Soul-Sword, which has the ability to destroy demons and other supernatural creatures. This revelation puts her in danger as various parties seek to control or destroy the sword.
4. Sebastian Morgenstern: Clary's brother Sebastian, also known as Jonathan, resurfaces as the main antagonist of the story. It is revealed that he is allied with the Dark Council and has been manipulating events to serve his own nefarious purposes.
5. The Wild Hunt: The Wild Hunt, a legendary force of spectral riders that can capture souls, becomes a significant threat to the Shadowhunter world. Clary and her friends must face this ancient darkness and find a way to stop its destructive rampage.
6. Dark Secrets Revealed: Secrets from the past come to light, shedding new light on the characters and their motivations. Clary's connection to the Shadowhunter world and the nature of her powers are explored in greater depth.
7. The Infernal Cup: Clary and her friends embark on a quest to find the Infernal Cup, an artifact that could potentially resurrect the angel Raziel and alter the very balance of power between Nephilim and demons.
8. Sacrifices and Heartbreak: The book features moments of intense emotional conflict and heartbreak as characters are faced with difficult choices and personal struggles. Sacrifices must be made, and lives are lost in the battle against the forces of darkness.
9. The Final Battle: The story culminates in an epic battle between the forces of good and evil, with the fate of the Shadowhunter world hanging in the balance. Clary and her friends must confront Sebastian and his allies, using all their strength and abilities to defeat them.
10. Uncertain Future: The book ends with uncertainty about the future of the Shadowhunter world and the characters' personal journeys. New challenges and possibilities await them as they navigate the aftermath of the events that unfolded in "City of Lost Souls."