Finding Clarity

Clara and Magnus strolled through the park, arm-in-arm. She admired the beautiful scenery before finally speaking up.
“Why did you ask me to come with you? I assume it’s not just for a leisurely stroll.”
“You’re here to meet Alexander.” He replied, trying to hide the smile on his lips. Clara raised her eyebrow and grinned at him.
“Why, Magnus Bane! You’re smitten!” She grasped his hand affectionately as she laughed. “Tell me more of him, love.” She insisted. As they walked, Magnus began to describe his boyfriend.
“Alexander, he’s a Shadowhunter, a Lightwood, in fact. His hair is as dark as the night sky above your home in Idris, with no stars and no moon. His eyes… I can’t describe the color of his eyes; you’ll have to see them for yourself. He’s intelligent, handsome, and protective of his family. He’d do anything for his sister and Jace. Ah,” Magnus brought his hand up to indicate two boys standing by the edge of the lake. “There they are.”
One boy was dark haired, thin and kind of muscled. She assumed that was Alexander, because the other boy, his hair was golden, he was taller and much more muscled. She froze in place when they turned around, her heart stuck in her throat.
“Clara, meet Alexander Lightwood and Jace Herondale. Boys, meet my old friend, Clara Carstairs.” The smile disappeared from his face as Magnus studied Clara’s reaction to the two young Shadowhunters before her. “Clara?” His voice lowered.
“Will.” She choked out, eyes glued to Jace, a perfect copy of her old friend.
“What is she talking about?” asked Jace, confused by the way this girl he’d never met before looked at him, as if she’d known him her whole life.
“You’re a Herondale.” She clarified, clearing her throat. “I was good friends with your ancestors, Theresa and William Herondale. They were my only friends, aside from Magnus and Jem.”
“If you don’t mind me asking, what exactly are you, Clara Carstairs? Will and Tessa Herondale have been dead for centuries. You don’t look like a Warlock, and you’re not a vampire.” Jace asked, a skeptical look clouding his expression.

“Cursed, Jace. I am cursed, though the answer you’re looking for is Shadowhunter. I am one of you.” Alexander’s eyes widened, and Jace’s gaze hardened.
“Shadowhunters don’t live that long.” He snapped, the disbelief clear in his eyes as he stepped closer.
“Back away, Jace. She is cursed with an immortal life, she cannot die. The ultimate Shadowhunter; indestructible.” Magnus interjected, releasing Alec’s hand to step closer to Clara.

“You’re her.” Alec’s voice broke the silence as recognition washed over him. “There was a story, in one of our textbooks, of a bloodbath that no one survived, except for one Shadowhunter, because she couldn’t die. All that was said about her was something about clarity.”
A sad smile crossed her face. “I like your boyfriend, Magnus. Alexander and Jace, they remind me of Jem and Will. Jem did the textbook work; William did most of the action.” She looked at Alec. “It mentions clarity, because that is my name. Clarity Jocelyn Carstairs.”