Summary: When Will and Jem are kidnapped during a routine investigation of missing Downworlders, they are thrust into a world they never expected to exist and meet the strangest girl they've ever known. An AU in which Mortmain doesn't hold a grudge against the Shadowhunters and never creates the automatons. Instead, he is the owner of a Downworlder galdiator-like boxing ring.

London

September 1878

The lights were magicked; they were too bright to be torchlight and have somehow managed block out the audience from view, but even so, Tessa Gray can tell that there were hundreds of people here tonight. She couldn't see their faces as she stepped into the ring, but she could hear the roar of their cheers after the Magister announced her name. Some were cheering for her-they're the ones that have placed bets on her winning-but some were shouting obscene things, things that used to make her blush and cringe. Their voices were visceral and cursing her and calling for her death, for her opponent to rip out her entrails, for her opponent to rip off her clothes, it doesn't seem to matter to them as long as she's being ripped apart. Some of the voices aren't even human and the howls, shrieks, and cackles made her skin crawl, even after six months.

She'd been doing this for six months. The realization made her cringe, a reaction she quickly smoothed over into impassiveness. She was getting better at hiding her weaknesses these days. It has kept her alive in the ring. She sent a prayer of thanks to Aunt Harriet for teaching her to hide her tears. Tears were a luxury she cannot afford here.

The lights flashed as her opponent was announced: a werewolf, with a name she doesn't recognize. She can remember when she first arrived here and first learned about the Shadow World. She had been mortified by the volley of new information that was thrown at her: that she shared the world with vampires, werewolves, faeries, warlocks, and demons. Terrifying creatures who were capable of terrifying things. She had spent the first week here paralyzed with fear.

That was before she discovered that she was capable of terrifying things.

The man entered the ring, a savage expression on his face. She was relieved that he's still wearing his human face though. She has never had to fight an actual wolf, but she has seen others training with one and it is not an experience she wants to have. When the man saw that she was his opponent, his savage expression became a sneer. She met his gaze with an even stare of her own, calm in the face of the storm of the ring. Her experiences in this ring have taught her that an even expression and steady eyes unnerves most contenders, and that it works in her favor to unnerve her opponents before the round starts.

She had spent the first two months here training. Learning what she was, how to Change, how to fight. It had been excruciatingly painful and mortifying enough to give her night terrors. Learning how to wear another person's body had been horrible in it's own right, but learning how to fight in that body and knowing, instinctively, the things they knew, responding, instinctively, the way they would have was even worse. She felt things she hadn't thought herself capable of: rage and bloodlust and the kind of fear that forced you to fight instead of run. She hated all of it.

She hated it, but when the first bell rang, she drew on the skills she'd reaped from the others. It's another trick that has kept her alive these past months. They circled each other, each sizing the other up, looking for weaknesses. She made sure that he didn't see any of hers. He snarled and lunged for her. The crowd roared, but she barely heard them over the pulsing of blood in her ears. She blocked his punch and struck him back in the same move. He had underestimated how strong she was and the blow caught him off guard. He reeled back, clutching his cheek, and the members of the audience who have bet on her shriek with delight: she has drawn first blood.

The man's face twisted in rage and he began to throw a volley of punches at her, disregarding the careful approximation of her from moments before. His blows were powerful, but sloppy. She blocked some and allowed others to land on her. The crowds generally loved it when she bled and the one gathered tonight is no exception. When he struck her hard enough to knock her down, she allowed herself stay there for a moment. There was a dull ache in her side from where he struck her, but his blood was on her hand still and she finally used it now.

The ground shook beneath her and she is close enough to the edge of the ring to feel the magic surrounding it throbbing with the crowd's energy as they realize what's happening. The Change rips through her body and her clothes tear as her shoulders broaden and her waist grows. She shrieked in pain, but the sound is drowned out by the crowd. This was what they've come to see after all, and she did not disappoint. The rumors of the shape-changing fighter were true and she was a novelty for them to observe.

When she rose, she could see and feel the man's confusion, but she shoved it back into the recesses of his own mind, not allowing it touch hers. When she hit him, he tried to block her, but weakly. She makes contact with his face. No one has informed him of her ability and he was suddenly afraid. She realized that he was a new werewolf, only recently bitten and her heart ached just a little for him. He had no idea what she was or how this world worked and now he was stuck here with her.

His fear made him just as sloppy as his rage. Now she, on the other hand, wore his very strong body, and while she has none of his rage to power her movement, she had control and precision and the element of surprise. The combination allowed her to win the match easily.

When he lost consciousness, she felt it, and let go of the Change. It shrank into her core and her body belonged to her once again. Her clothes were shredded to ribbons, her ribs ache, and she tasted blood in her mouth. The crowd was in a frenzy and the already too-bright lights flared even brighter now that the round was over. She was dizzy from the aftermath of the Change and the aftermath of the fight. When the Magister appeared in his customary puff of red smoke to take her hand and lift it over her head in victory, he practically had to hold her upright. It made her feel sick to have him touching her and that was enough to force the strength into her legs and spine to keep her from leaning on him until the lights dimmed and he dropped her hand.

When the Dark Sisters collected her and pulled her from the ring, they had to hold her up between them. She doesn't particularly like it when they touch her either, but it's better than having the Magister support her weight and her ribs hurt. They were both pleased with her, which means that her fight has brought in a lot of profit. Mrs. Black was saying something about how she was fast becoming quite the main event and how they could start charging double for her fights when Tessa lost consciousness.

October 1878

"You'd think the Downworlders would learn to be a bit more careful," William Herondale stated as he and his parabatai wander through Billingsgate Market. It's late, and the fish market has long since been closed, but the smell of this morning's catch is still heavy in the air and the cobbles are slick with river water and fish guts. James Carstairs, who has been peering down a dark alley, practically glows amongst the gathering mist, but doesn't look at him when he replies:

"You'd think that the Downworlders would have had a case of demon pox by now if they weren't already being careful. Something's not adding up."

The dark haired boy made a face behind Jem's back and follows him down the alley. "Which is why we are out here for the third time this week. We must prove that demon pox is a real threat before Charlotte and Henry return."

"Or," Jem started as he pushed aside a stack of crates to reveal a door carved with the double ouroboros they'd been looking for. "Perhaps we might, you know, find a clue as to what's happened to the Downworlders who have been going missing these last few months and whether or not their disappearances have anything to do with the Pandemonium Club."

Will withdrew his stele and drew an opening rune, taking his place as lead while Jem covered his back. The door swung open silently, revealing a dark hallway. He put his stele back in his belt and replaced it with a seraphic blade, murmuring its name as he pulled it from the sheath. The blade blazed like lightning, illuminating the corridor before him. The corridor extended only ten feet in front of him and was cool enough inside for the mist to make its way in without vanishing, giving the space an eerie feel. He entered the building warily. Behind him, Jem has drawn his own weapon and added to the light, following him. The corridor leads to a large, but empty, room made entirely of dark brick. There are no windows and no furniture, the mist hangs heavily on the floor.

"Will…"

"I know, I know. It was a false lead. This place hasn't been used for anything in a hundred years.

"No, Will. I think-"

"Damn witches," Will murmured, ignoring his parabatai. "Should have known that-"

"Will, goddammit, turn around!"

He spun around in exasperation and nearly dropped his blade in shock. Jem's back was to him and beyond him were at least half a dozen Iblis demons, their teeth glittering in the light of the seraphic blades, rapidly forming from the mist. He recovered quickly, the cold of battle settling over his shoulders like a well-worn jacket. He withdrew a second blade and named it before racing to Jem's side.

Or, at least, that was his intention. The reality of it was that several more demons sprang up from the mist and blocked him from his parabatai. In reality, it took him several minutes and half of one of his blades to get to Jem. The trouble of Iblis demons, he decided, was that they were bloody stupid, but were also innumerable. Every time he cut one down, another took it's place.

They don't need to talk to end up back-to-back. It's all instinctual and neither one is surprised to realize that the other is suddenly at his back. They fight beautifully together-both performing opposite sides of a deadly dance they've practiced every day for years. They've fought Iblis demons before and have practically choreographed the steps it takes to kill them. Will considered composing a poem about the experience as he and Jem take turns cutting the arms off one before Jem delivered the death blow, covering them both in a spray of ichor.

Jem was in his element tonight, all silver and blue light as he wielded his cane-sword and seraphic blade in perfect synch. Will recognizes the same cold of battle in his friend's eyes and grins to himself. His brother looked more alive in this moment than he has in ages. The color in his cheeks was healthy, though he was breathing heavily, which concerned Will a bit. However, things had been quiet at the Institute lately, and this was the first real fight they've shared in months and they both relish in it.

They have nearly finished off the Iblis demons when Jem swore, loudly and dropped his sword. There was a moment where the room spun as the light from the blade skittered across the floor and then winked out. Will cut off the head of the demon he was fighting and turned around in the same movement. A Ravener demon had Jem caught up in its grip, his arm twisted painfully behind him as he struggled to free himself.

"Will!" his parabatai's voice was strained. "Behind you!"

He realized too late that the Iblis demons had just been a distraction to keep them too busy to notice the arrival of the Ravener demons. Likewise, Jem's warning was an instant too late. The crack of exoskeleton on bone filled the room as the demon's tail made contact. There was a sharp pain in the back of his head and the last thing he saw was Jem's face stretched in pain before the room went completely dark.