Hello my lovelies! This is my first ID/ TMI crossover- so excited to post this!

Warnings: This does contain spoilers from CoHF, but the plot here is slightly changed due to adding characters not from this time- so if you're not up for spoilers then don't read of course!

However, I won't be following the book to the mark and there will be a few added things that I will pop in here and there.

Disclaimer: I don't own the Shadow World. If I did, the Herondales and Carstairs would all be mine, and I would be Magnus.

Lunch at the Institute, as it had been for the past couple weeks, was a quiet affair. The excuse everyone silently agreed on were their personal recuperations from their last automan attack.

It was true, to some extent, that the inhabitants of the London Institute were just too tired to do much, and the only thing that seemed to apparently brighten the mood was talk of the wedding.

The wedding.

Will nodded and smiled at appropriate times, politely, as Charlotte tittered on and on about Tessa's gown and how beautiful she would be in it, and how the decorations would just pull together, and how everyone was going to be so dashing and beautiful-

Of course she'll be beautiful, Will wanted to interject as snidely as her could, but bit his lip in the effort to restrain himself.

Guilt washed over him at his need to do so, the ripples becoming a wave as he glanced at his parabatai. Jem was shaking his head at Charlotte's ramblings, but his eyes and grin were focused directly on Tessa, who returned the same gestures with equal love and mirth.

He hadn't seen her smile in a long time, not since Nate, and since the business with the elder Lightworm, he'd barely seen her at all.

He felt a kick at his shin and scowled to hide the embarrassing pain that shot up his leg. Cecy smirked at him across the table, a look that morphed to concern. He cocked a delicate eyebrow in question and she indicated to the couple next to them.

Will's scowl deepened.

He couldn't excuse himself fast enough when lunch was over. Debating going outside, he floated near the doorway. A questioning look from Sophie turned him away. Wandering the hallways, Will sighed, raking a head through his hair.

It seemed nothing wanted to play in his favour, but couldn't bring himself to be truly grateful for the one person who had anchored him and kept him sane all these years.

He was a horrible man, maybe he deserved what he was getting. He was stupid, selfish and now it was all catching up to him.

Glancing up, he noticed that in his little time berating himself, he'd wandered straight to Tessa's room. Cursing in Welsh, he moved to leave, as hastily as possible, when the undeniable, horribly familiar coughing started from the room across.

Fear racked Will as he entered the room. He prepared for the worst, but it would be the end of everything if he was ready for it. Thankfully, Jem was still conscious, at least.

He was seated on his bed, back to the door. Hunched, his body racked painfully with harsh coughs and wheezes. His shirt was half on, maybe half off, but it didn't matter. Will could feel the ridges of his spine and ribs even more now, as he sat next to his parabatai and placed his hand on his back, rubbing as if it would soothe him.

Jem relaxed under his friend's touch, and tried to sit up but was forced down by a new fit.

"Wh-Where's Tessa?" he forced out.

"Not here, I can-"

"No, no. Don't." Jem replied hastily. The coughing subsided and he could sit up. Eyebrows knotted in concern and worry, Will protested as the other man stood. "I'm fine, Will." Jem muttered as he grabbed a handcloth to wipe his hands.

Will felt sick seeing the white fabric stain red. Jem's eyes were soft as they met his.

"How much have you left?"

"Will-"

"How much?" Jem sighed, raking a hand through his silver locks.

"I've been using it more often. I may have enough to last maybe the next two weeks but- Will, where are you going?

"To tell Charlotte you are to be on house rest-"

"You're doing no such thing."

"I am going to do such a thing!" Will raised his voice, whirling around. Jem stepped back, palms up. "You can't keep wasting your energy like this- your supply is almost out, and then what?"

Jem relaxed and sighed. He smiled ruefully.

"You know what, William." He said tiredly, with a little impatience.

"How can you be so crass? Do you not care if you love or die anymore?"

Jem stared at Will before turning silently. As he button his shirt he grabbed his jacket and cane.

"Jem."

"I'm not listening to this right now, William, and I am in no mood to fight." He answered plainly before swerving past the dark haired boy.

The silver-eyed Shadowhunter moved much faster than the Welshman suspected; Jem was out the door before Will had even reached the main hallway. Cursing, he ignored Charlotte's questioning and ran outside without his hat or jacket.

It was nearly a quarter to the next hour before Will managed to find Jem wandering aimlessly along the Thames.

"James!" Will called, repeating the name until Jem finally turned around in annoyance.

"Will, please-"

"No, you listen to me."

He continued walking but didn't protest. Will caught up and fell in step with him.

"James-"

"Will, look-"

"No, you listen to me- that was the agreement." Will whined.

"No, you idiot, look, over there."

Exasperated, Will glanced to where Jem was pointed and spotted the man with the remarkably green eyes. Demon.

Without anymore words, Will split away from Jem and stalked the prey as it moved into an alleyway. Will smirked- easy kill.

Deciding so, he brazenly followed the demon, seraph blade tucked neatly an ready to be unsheathed.

"Well, hello there. Wrong day for a walk-about, I think." Will greeted mockingly at the figure.

The demon turned, but to Will's surprise, with triumph rather than fear or surprise.

"Is it?" it answered mockingly "Now where's you little friend?"

Tensing, Will drew out his blade and called its name, the blue light flaring from the hilt of his blade. Jem stepped out from the darkness, his own weapon alight and ready for a fight.

At that moment, the demon began cackling- a horrendous, high-pitched sound that could be the stuffs of children's nightmares.

"Something caught your throat there, old chap?" Will mocked, "Better quiet down- we don't need babies crying now, do we?"

A bright light cast on its and Jem's face then: a bright blueish-white ray accompanied by some wind that almost knocked Will over.

"Do tell the Master I send my regards," the demon grinned, sharp shark-like teeth in the place of a human mouth bared themselves at Will.

"Wha-"

And with a tremendous force, Will was shoved through the open portal.

.oOo.

The portal reopened, throwing Will at least five meters into the real dimension before he hit the ground. A hard rocky surface scratched at his porcelain skin roughly, but Will focused on not being sick all over. He was usually a good Portal-jumper, but this was something else.

Coughing, he got onto all fours and held his stomach, turning without grace when he heard a thump next to him.

The Portal slammed shut after spitting out Jem, letting the air still. The half-Chinese Shadowhunter got up with a little more grace than his parabatai hand and offered a hand to help him up.

"A little bit nauseous, are we, Will?" Jem asked, his lips quirking upwards.

"Please," he retorted, rolling his eyes. "Shut up." He added with more force upon noticing Jem trying to stifle his laughter.

For the first time, Will took in his surroundings. Jem's laughter died in his throat.

"Where are we?" Will asked "Is this hell?"

"I don't think hell looks like London." Jem muttered.

Will turned in a circle, and then looked down.

"Why are the pavements black?" There was a terribly loud noise then, and Will glanced up to see and enormous carriage, without any bloody horses, hurtling towards him at an ungodly pace. "By the Angel-" he swore, stepping backwards as it literally flew past him.

If it weren't for his developed reflexes, he'd have been one of Sophie's pancakes on the ground. Trying to calm his heart, Will stepped further away from the black danger-zone and onto the grey concrete work. He noticed pedestrians keeping to this colour.

"What-"

"I don't know, but I think we should find answers."

"Brilliant notion James, and where do you propose we get those answers? I remember this wonderful tavern nearby- I know the barmaid- where are you going?"

Having to jog to catch up, Will scowled heavily at Jem.

"We're going to the Institute."

"The where?"

"The Institute." Jem pointed, indicating to the old structure down the road, an anomaly next to the glass monstrosities around them.

.oOo.

They barely made it into the gates when Jem noticed the familiar blonde figure sat on the steps, staring aimlessly into space

"Jess?"

The blonde whirled at the sound of her name, a look of pre surprise etched on her face upon noticing the two boys in front of her.

"What the hell?" she cried after a second. Will raised an eyebrow at her lack of mannerisms.

"Well hello to you to-"

"No, seriously, what are the two of you doing here? Are you dead?"

"What? Jess, that is absurd." Jem retorted.

Jess open and closed her mouth, as if trying to figure out what to say. It was then Will noticed.

"You aren't really here." Jem turned his gaze to Will.

"What? Have you two both gone mad?"

"By my hatred of ducks." Will murmured "Jessamine, are you a bloody ghost?"

"William!" Jem hit his companion in the arm, affronted for the girl by his rudeness.

Jess, meanwhile, looked between the two apologetically.

"Jem, that- that's true." When she received no response, she continued, "Do you two know what year it is?"

"Eighteen-sixty-seven."

"You're just a teensy bit short."

"Teensy?" Will snorted.

"It's two-thousand-and-eight." Jess offered, ignoring Will.

"Yes and I am a friendly, fluffy talking duck. Very funny, Jess."

The blonde huffed "Look around you. Do you see what this is? All these new buildings, the lack of carriages, the roads- it's called urbanisation. Modernisation. For some reason you idiots found yourselves over a century in the future."

Will snorted again, but was silenced by Jem's hand on his shoulder.

"William, I think she's right." He murmured. Will glanced around, admitting (never aloud) that this may have been the case.

"Well then, Ms Ever-Knowing, what is our solution."

"I'm a bloody ghost, Will, I don't know." Jess hissed "But you can't be seen by more people, if the movies are true-"

"What are moo-vees?"

"Shut up, I'm trying to think."

"That's a first." A glare from Jess silenced him. "Wait here." She muttered curtly before vanishing.

Reappearing minutes later, glare still etched on her face, she huffed.

"You boys are lucky I'm even here."

'What are you even doing here, Jess? Last we saw you were fraternising with the enemy."
"Will-"

"No, he was right." Jess sighed "You obviously don't know what happened after that, and I don't think I can tell you anything you don't know." She paused a little, frowning "But you must know I regret everything,"

Jem moved to say something, but was cut off by Jess looking past him.

"Your help is here. You can leave now. Shoo." Jess flipped her wrists at them, trying to make them leave "Hurry up, before Arthur sees you."

Jess followed them to the gate and promptly disappeared once they were outside. They were greeted by a albino-haired, blue-skinned woman glaring at them.

"Why do the women of this time insist on glaring- it doesn't sit well with your features." Will stated.

"Herondale, obviously."

"Obviously? What do you mean ob-"

"Okay, please shut up. You are incredibly lucky I was running errands here today or you would've been in a hell lot of trouble, do you understand me?"

The Shadowhunters noticed for the first time that the warlock was in trousers. In public- and while they could see the shimmering glamour shifting her skin tone, they could knew it didn't disguise her attire. Noticing them staring, she grinned.

"It's a new age, boys- welcome to the twenty-first century."

.oOo.

"Not a Portal-jumper are you, Herondale?"

"I am perfectly fine, thank you very much." Will glared at the lady, making faces behind her back as she led them on.

"Where are we?" Jem asked, still unsure about the warlock, despite her convincing them she knew Magnus Bane.

"I told you, I'm taking you to Magnus."

"Is he the one who sent us here?" Jem asked.

"If it is, I'll drown him in a lake." She smiled "We have enough problems with that freaking-" she sighed "You're his problems now, either way.

She led them up a building, walking a few flights of stairs until they reached a door.

With her knuckles, she delivered three sharp raps to the door. A few moments later, she did it again. Once again receiving no response, she rapped again, this time harder.

"Maybe he isn't-"

"Trust me, that melodramatic bastard is home."

"The language of the thirty-first century is appalling."

"Twenty-first," the warlock corrected as she knocked again.

Finally the door swung open.

"I swear on Lilith, if it's one of you here again-" Magnus paused, noting the company was not who he expected. He sighed "What do you want, Catarina?" he asked with hostility, though he opened the door wider.

"Not me, exactly." She called as he walked into his apartment. The warlock- Catarina- followed, and beckoned to Will and Jem to follow. "More like a blast from your past."

"If those Nephilim or the Daylighter is here, tell them they can take their speeches and shove it up-"

"Please Magnus, no details."

Will looked around the absurd room. Everything…glinted and sparkled like a little girl's gown. Literally, there was glitter on everything- the walls, the tables, the cat residing on the couch. Magnus re-entered the room and instantly noticed the two new faces and froze.

Jem and Will took in the warlock's new get-up. His trousers were extremely tight and leather, for some ungodly reason. He was barefoot, and his toenails and fingernails were painted black. He was wearing women's cosmetics, especially heave around the eyes, though it seemed to have smudged down his face. His hair, dark, flat and ungroomed glittered slightly from remnant sparkles.

Magnus' eyes widened exceptionally, his cat-like slits broadening in recognition. His lips formed their names quietly and he took a step towards Will, arm lifting.

"What-" he croaked, before clearing his throat "What in the name of Lilith are you doing here?"

.oOo.

"What do you expect me to do with them?" Magnus asked as he paced in front of his three, rather unwelcome guests.

"I don't know, find them a way back, maybe?"

"Oh yes, and I'll just go resurrect the dead while I'm at it, am I right?" he snorted angrily, quickening his footsteps.

"Well, what else are we supposed to do with them?"

"Them, are sitting in the room with you." Will retorted snidely.

Magnus shifted his gaze to Will's challenging blue depths for the first time since the initial 'reunion'. It had been so long since he saw those eyes, yet just recently there was another pair so similar to-

Snapping his head away he bit his lip.

"I don't know any time travelling spells. I don't even know if there are any even in existence-"

"Obviously there are if they are here."

"And you want me to look for it. Yes of course, it isn't like we're amidst a war or anything."

"Oh come on Bane, since your break-up with that Nephilim boy, you've been doing absolute squat-"

"Squat?" Will interjected, "I apologise, but the terms you use-"

"Look, they're your friends, and Herondales are a new level of irritating-"

"Hey!"

"-and this may take your mind of things, so please?"

Magnus glared between his friend and his old, long-dead ones before sighing in defeat.

"Leave before I change my mind."

Catarina smiled, and pecked the other warlock on the cheek- a gesture she rarely did unless he was rock bottom emotionally.

"If anything, we'll just run off to Peru."

"I'm banned, remember?"

"Rio, here we come, then." She chuckled before leaving the flat.

Magnus slowly sat himself down on his armchair, watching as his cat snuck up to Will and climbed up his leg, much to the boy's surprise. Leaning in close, Chairman realised that this was the wrong brunette and hissed before settling on the other, more comfortable stranger.

Jem smiled, scratching the feline behind its ears as Will scowled, brushing of the imaginary hairs of his trousers. Noticing how inappropriate their attire was, the warlock sighed immensely.

"Before we get to the real business, you two really need to change- you look like you've come from the god damn Renaissance fair."

.oOo.

There was a lot of yelling and clothes thrown back and forth between Will and Magnus. It seemed anything mildly body-fitting was surprisingly unwanted, to say the least, by the self-confident Shadowhunter. Jem merely requested for anything without glitter, but that was out of the question.

Sighing for the millionth time that day, Magnus slammed his wardrobe shut.

"How can the two of you be so goddamn picky?"

"How are all of your clothes either strewn with glitter or five sizes too tight?" Will retorted.

With a huff, Magnus opened the final wardrobe and turned to them.

"He's about your sizes. Pick what you want and be quick about it."

With that, the warlock rushed out of his room.

Finally settling on the plain black, incredibly soft, cotton shirts with half-sleeves and the rough, yet comfortable dark trousers, Will and Jem re-entered the living room.

"Looking like true modern Nephilim." Magnus muttered loudly. His gaze lingered on Will a little longer than it should have, and he looked away.

"Who's clothes are these?" Jem asked, curious. Magnus spluttered, as if surprised by the inquiry.

"A friend." He answered slowly. Will looked Magnus up and down, noting the way the warlock had eyed the clothes in wardrobe when he flung it open.

"You love him." Will stated; it was a look he saw in the mirror everyday.

Jem looked between the two, and then at his attire.

"And he's a Shadowhunter."

"How smart." Magnus answered snidely "Now what are you going to say- how wrong it is? Come on then." Jem shrugged.

"I am just…sorry that you have to go through something like this. I can't imagine the pain." Will's lips twitched at the irony.

"Yes," he echoed, "can't imagine it at all."

Magnus looked at the broken boy in front of him, green locking on blue. He smiled ruefully then, knowing that at least one of them would have the happy ending.

The silence was broken by the hacking coughs.

Jem was on his knees, and suddenly Will was next to him. The former was wheezing, trying to form words Magnus couldn't comprehend, even when he was kneeling in front of him himself. Will, however, seemed to understand completely, and raced into Magnus' room.

Magnus moved to where Will was, and grabbed a tissue from it's container on the coffee table and moved it to Jem's mouth. It was saturated scarlet within moments.

Offering soothing words, Magnus reached for more tissues when Will sprinted out, a rolled piece of paper in his hands. Magnus knew instantly what it was- it was a long time before he'd seen the drug.

Unrolling it, Will forced the paper to Jem, who with shaking hands, tipped the white powder into his mouth. His breathing evened, and his coughing reduced after awhile, though his body remained weak.

It was then Magnus realised, that he had to get Jem back to his time if he was to survive.

"Jem," Magnus started softly, "I'm sorry but your medicine hasn't been sold for the past century."

Jem's coughing subsided to silence, save his ragged breaths. Will's eyes met the warlock's again, but this time unshielded fear were in those azure orbs.

Magnus made to say something, anything, when the doorbell rang.

Hastily, the warlock made to the door, ready to tell whoever it was to fuck the hell off, when he looked through the peephole.

"Shit." He swore aloud.

"Who is it?" Will whispered, the demand evident in his hushed tone.

"Someone who really can't see you."

"Who?" Jem coughed; Will hushed him as he guided him to the couch.

The doorbell buzzed again.

"Who is it?" Will asked again.
"One of your more insistent descendants." Magnus replied, after a pause. "I was trying to keep this from happening, but it already failed before I could get started." He continued, mostly to himself.

"One of my-" Will broke off, suddenly keeping his gaze on the door.

The doorbell buzzed a third time.

'If he is my descendant, as you say, wouldn't he be willing to help?" Will asked.

"Trust me, the past two generations of the Herondale line hasn't been very staraightforward."

"That doesn't matter," Will answered, though the comment set him at an unease "I am certain, if he is anything like me, he would help."

"He is, quite a bit-" Magnus broke off "No, I'll just tell him- no, he'll be too suspicious, that boy can never leave things be."

"Definitely a Herondale." Jem wheezed.

"Very funny, James." Will said affectionately, a small smile on his face "We have to take the risk that he won't help us. We need to get back to your time."

The bell buzzed, once again.

Magnus looked between the two, before letting out a breath he didn't know he was holding.

"Fine, but don't say anything, unless I allow it. Understand?"

Will nodded, urging him to hurry up. Jem sat up straighter. Magnus began to open the door, but paused.

"No comments on the topic of our conversation. Understood?"

"Understood, Magnus." Will hissed with exasperation.

Magnus nodded, before taking a breath. With a flourish only Magnus could manage, he flung open the door.

"What are you doing here?" he demanded to the figure on his doorstep.

"My, my," Jace said, smirk in place, "so unwelcoming."

What do you think? Do review I love reviews 3

-Ash :)