I know, I know, I should be working on my other fanfic, not writing a oneshot for another fandom. I will start on the next chapter of the 'essence of Truth' shortly (I was delayed due to a an unfortunate event involving a cup of hot chocolate and my laptop). My only excuse for this oneshot is that this was in fact written for a competition and I thought peps might enjoy reading it.

- Weiryn

EDIT: having just read the City of Heavenly Fire and re-read the Infernal Devices, I decided to re-write this one shot. There aren't any real spoilers for CoHF but I've adjusted some parts to be more in line with canon.

Note: Cassandra Clare owns the Infernal Devices and the Mortal Instruments. Not me. Even though I would love to.

The problem with immortality is that the world changes and you don't. People grow old and die, empires rise and fall but you just stay the same. Some days, I'd say it's the greatest gift you could ever have in the world…and on others, the most horrible curse that you could ever have. I just wish I'd had a choice.-

- excerpt from the diary of Tessa Gray

Being immortal doesn't make you invulnerable - tougher than the average person, defiantly but not invulnerable by any means. However, Tessa Gray had an unfortunate habit of 'conveniently forgetting' that fact. It was a habit that had a tendency to get her in trouble, as was the case tonight.

She hadn't planned on it. She'd only wanted a fun night out at the Pandemonium club. Of course, she'd been deluding herself. It was a long established fact that she, Theresa 'Tessa' Gray, attracted trouble like a pulse attracted vampires. So she really shouldn't have surprised when she got herself into trouble once again.

Tessa made her way to the exit of Pandemonium. She hadn't planned to come out tonight – these days she spent most of her time in the Spiral Labyrinth. Nonetheless, her friends had dragged out, and she was glad they had. She'd had a good time tonight. She'd meet up with a few other downworlder friends, had a couple of drinks, and danced a bit. Strobes flashed, casting strange silhouettes on the walls. In front of her, countless people danced to the music – if you ould call it dancing.

Having been born in the 19th century, she still couldn't help but feel dancing should involve actually dancing, rather than swaying and grinding – something that took no skill at all. Taking a deep breath, Tessa made her way through the heaving mass of bodies. The music throbbed like a drumbeat, so loud that the brunet could barely think. Once, she would have avoided a place this like the plague. However, it's impossible to avoid clubs forever when one of your closest friends is Magnus Bane, High Warlock of Brooklyn and King of parties, glitter and drama. He had dragged her out so many times that she'd grown to actually like it – not that she'd ever tell him that. Pandemonium was the best of the lot – plenty of Downworlders came here and considering the number of unusual hair colours, strange tattoos and piercings, they fitted right in.

Finally, she stepped in the cool New York air, shivering slightly at the temperature drop. Time to head home.

"Hey babe. You wanna come party with me?" A hand thumped down on her shoulder, heavy and unwelcome and she turned to meet the leer of a teenager whose face was more piercings than skin. Tessa wouldn't help but wince as his breathe washed over her face – it stunk of alcohol – and the fact that his eyes were most defiantly trained not focused on her face.

"No thank you. Now please let go of me," she said, trying her best to be polite. With guys like this, getting angry with them was the wrong course of action – they'd just get angry right back at her and then she'd be in a right fix. If things went her way, he'd just let her be and she'd catch a cab home and things would fine.

Of course, nothing in her life was ever that easy.

"Don't you say no to me, you bitch!" The guy's voice rapidly shifted to angry, lips contorting into a scowl as his hand tightened on her shoulder hard enough to bruise. 'Definitely drunk,' Tessa reflected in the small part of her brain that wasn't panicking, 'and not happy either.'

Reaching up, she grabbed his wrist with her hand, digging her nails in his flesh. "Let. Me. GO," she growled, her stormy grey eyes narrowing, "Don't make me repeat myself."

"Or what? You'll kick me on the shins?" he laughed, harsh and mocking. As he spoke, his eyes began to change slightly, becoming amber and far more animalistic. Werewolf. Tessa gulped, suddenly realising how much trouble she was in.

Why did she have to be the only warlock on Earth unable to use magic? She'd really love to be able to throw a lightning bolt right about now. Still, she did have her on unique set of skills.

Taking a deep breath, she made herself Change. It started as an itching sensation the swept across her body and then suddenly she was getting smaller as she took the form of a small girl she'd met over a decade ago.

The werewolf yelped as the flesh beneath his hands twisted and loosened his grip – just what she'd intended. Ripping herself free from his hands, she began to run. As she did, she shifted back to her own body. It was a skill that she'd perfected in the century since she'd discovered her ability and while she didn't often use it, there were moments such as this when it really came in handy.

Sprinting along the footpath, she heard the sound of footsteps behind her. Fear spiked through her and she increased her speed, lungs heaving for air. Racing around a corner, she came to a halt. Taking a shuddering breath, she stared at the brick wall in horror. Dead end. There was nowhere left to run.

"Come out little girly. The Big Bad Wolf has found you," said the werewolf, standing in the entrance to the alley, "your little tricks won't help you now," as he advanced towards her. Even as her fear increased, a small part of her wanted to laugh at his clichéd words.

"Good thing I will then," rung out an unfamiliar voice from the alley entrance. A figure was silhouetted there against the lighting of a murky street lamp. Tessa could see the glint of a dagger in his hand. The werewolf spun around, growling.

"Who're you to tell me what to do?!"

"As a Shadowhunter, I order you under to authority of the Clave to leave or face punishment," said the voice, raising the blade.

For a moment, she thought the werewolf would refuse but he obviously had at least half a brain because after growling in frustration, he stalked out of the alley, giving the figure a wide berth.

Breathing a sigh of relief, she slumped against the wall, suddenly exhausted. Closing her eyes for a second, he heard footsteps approach.

"Are you alright?" asked the Shadowhunter softly and Tessa nodded only to realise that in the dark of the alley he probably couldn't see her nod.

"Yeah. Just give me a few seconds." Taking a few calming breath, she straightened and turned towards the Shadowhunter. "Thanks for rescuing me. Normally I'm pretty good at looking after myself but like they say, everyone's luck runs out sometime," she said with a sad smile before beginning to walk towards to the main Street. A second later the Shadowhunter fell into step besides her.

"I'm Alec, by the way," he said to her and Tessa nodded.

"Tessa Gray. The only warlock on the planet unable to use useful magic," she replied and he laughed as the stepped back out onto the footpath. Smiling, she turned to see what her rescuer looked like only to freeze at the sight of an achingly familiar face.

"Will…" she breathed, unable to stop a torrent of images flooding through her mind: a dark haired boy standing shirtless in at attic, drinking holy water; the same boy in a drug den in the slums of London, trying to drown out the world; black hair hanging in front of sapphire eyes…only this couldn't be Will because he been dead over a century.

Blinking, she took another look at the teenagers face – because he was a teenager, no more than eighteen or nineteen. This time she noticed the subtle differences. There was a definite resemblance but this was a totally different person. As realisation dawned a blush spread across her cheeks. The fact that he was scowling at her didn't help either.

"I'm sorry. I didn't mean to call you that…I had a…friend, you see…a long, long time ago and you reminded me of him," she said, only just managing not to stammer. Frozen in place, she waited for him to say something. Finally, after a few seconds he relented and his scowl softened slightly – not into a smile mind, but it was better than nothing.

"It's alright. My boyfr- ex boyfriend, rather, used to say that I was the spitting image of an old acquaintance of his by the same name. It kinda annoyed me. Still does," he said, tucking his hands into the pockets of his jeans.

As he spoke, Tessa took a second to look him over and realised with a start that he wasn't really dressed for clubbing in his baggy jeans and jumper. She crooked an eyebrow in surprise. "You normally patrol the streets in those clothes?" she asked with a tone of scepticism in her voice. His response was a grimace.

"No. My sister dragged me out to Pandemonium to 'drown my sorrow'," he said, "she thinks that going partying is the answer to everything. Magnus did as well," he paused, running his hand through his hair, "I stepped out for a breath of fresh air and saw you run off with that werewolf following. I guess my instincts just kicked in 'cause I followed you."

Tessa barely registered his last few words because the moment he'd mentioned the name Magnus, her brain had blocked out everything else. Her mind was too busy racing as her she drew links between numerous facts whirling away in her head towards a surprising conclusion. Now, to confirm: "What did you say your last name was?"

Alec looked at her, slightly suspicious. "I didn't. It's Lightwood." He frowned when Tessa gasped.

"You're Magnus' Alexander, aren't you? He's always going on about you. Whenever I talk to him it's 'Alec this' and 'Alec that'…" Tessa ground to a halt at the look of pain in his eyes. "Oh." Suddenly she put together the little snippets of conversation into place – the mentions of an ex boyfriend and 'drowning his sorrows' finally making sense. Her lips twisted into a scowl.

"He broke up with you, didn't he? The bloody idiot. Over 800 years old and he manages to push away the best thing that's happened to him in years-"

"It was my fault," said Alec's quiet voice, "not that it's any of your business. How do you know him, anyway?"

"He's a good friend. Has been for over a century. He helped me when everyone else was gone…" she said, voice trailing off into silence. "Look, how about I buy you a coffee at a café I know as a thank you for saving me." She looked at him, eyes pleading and. The boy hesitated for a moment, before sighing and nodding.

"Lead the way," he said and Tessa set off down the street, Alec beside her.

An awkward silence fell over them that lasted the entire walk to the café – Esmeralda's Den – and Tessa ordering them their drinks. It wasn't until they had sat down on two squishy armchairs that took the place of traditional seats that Alec finally spoke up.

"An old girlfriend of Magnus' – Camille Belcourt– told me she knew a spell that would make a warlock mortal. I told her no but when Magnus found out, he told me he couldn't trust me if I would even consider something like that," he said, looking down at the mug of coffee in his hands. " I shouldn't have even considered it. If I wasn't willing to be immortal to be with Magnus, I shouldn't have thought he'd ever be happy being mortal with me."

As he spoke, Tessa looked at him with sad eyes, before reaching out and cupping his hands with her own. Alec looked up at her, surprised and Tessa smiled at him sadly. "There was once a time that I would have done anything to be mortal – to live out a normal human life. I didn't even know I was a warlock until I was sixteen."

"Why-" Alec began only to cut off by Tessa.

"The year was 1878 and I was sixteen. I had travelled to London from New York in search of my brother. Instead, I was tipped into a world I never knew existed – a world of magic and demons, Shadowhunters and vampires. I was taken in by the London Institute where I met two young Shadowhunters – parabatai – by the names of Will and Jem."

Alec's eyes lit with understanding. "The same Will that you and Magnus say I look like." The words had an edge of bitterness to them that Tessa didn't miss.

"The very same. Of course, the two of you couldn't be more different." As she spoke, surprise flashed across Alec's face and Tessa grinned, "From what Magnus has said, your friend Jace is more like Will, which in its self isn't that strange since Will was a Herondale as well." She chuckled at the shocked expression of his face. "You're more like Jem, in a way. Quiet and thoughtful," she said, sorrow tingeing her words. Her beautiful Jem.

"Jem?" Alec questioned.

"James Carstairs. The man I would have married. He was only nineteen when we lost him – we'd only be engaged for a few months. I've never stopped loving him to this day." Tessa gave Alec a sad smile.

Leaning forward, she looked straight at Alec. "As an immortal, it's terrifying to love a mortal. You fall in love with them knowing that your days together are finite, you watch them age while you stay the same, and then-" she broke of, pain raw in her voice. "It's the curse of immortality, you see. Even if you get decades with them, their lives are still mere blinks of the eye and when it's the people you love, it hurts all the more."

She shook her head, before continuing. "Magnus has pushed you away because, even if he won't admit it, he's scared. That doesn't mean he doesn't love you-"

"But he's angry-"

"Love and anger aren't mutually exclusive. I've seen him in countless relationships, including his one with Camille and trust me, you're the best thing that's ever happened to him, even if he doesn't realise it," she said with a wry smile. "I will guarantee that he's every bit as miserable as you are."

Pulling out a pen, she scribbled own her number on a napkin and pushed it towards Alec, standing.

"With a bit of persistence, I'm certain you'll patch things up," she said with not a trace of doubt. "But call me if you need advice," she said before turning to walk out of the café. Behind her, she could feel Alec's stare on her.

Just as she was about to step out the door, Alec called out: "Is it worth it?"

"Yes," she replied, stepping out the door into the night.

It was always worth it.