City of Heavenly Fire

Clary thought that with Jace's arrival, things could return to what used to seem normal at the Institute and at home. But with Sebastian running freely, new troubles begin to arise, hurling them back into another battle that threatens not only their lives, but all shadowhunters's as well.

Now struggling in the midst of impending war, Clary must accept that an ultimate sacrifice must be made.

Her.

"Clary, please," Jace begged. Anger burned in his eyes, but Clary knew him well enough to see the agony behind it. She wanted to comfort him; to make promises that she could keep to the boy she loved, but she knew what had to be done. Clary shook her head. "You have to do it!" she shouted, stepping away from him. "Now, Jace!"
"No! You can't make me!" he fired back. His eyes glistened with unshed tears and his entire body was shaking violently. Clary rarely knew Jace to look defeated, but that's how he looked, standing before her; vulnerable and broken. "Tell me to do anything else," he said. "I beg you, Clarissa. Anything else but this."
She felt her own eyes well up, silent tears spilling down her cheeks. "I'm sorry, Jace." She took another step backwards.
"Clary, no!"
She turned to face him one last time. "Don't let Valentine's story be true," she said, her tone desperate. "Don't let this destroy you."

(All characters and original story belongs to Cassandra Clare. This following up idea I made; it is my fanfiction on how her next book could go)