A/N: This story will contain violence, some gore, and bad language.

This is how it ends, she thought, as it should.

Rath scrambled up the statue's arm, her Nightingale boots gripping the ancient stone silently. It wouldn't have mattered if she'd been wearing iron; the water gushing from the burst pipe in the ceiling filled the stone chamber with noise and only the loudest of sounds could cut through it.

She wouldn't hear him coming, and he wouldn't hear her.

She scrambled up onto the shoulder, sparing only the briefest glance at the serene, now eyeless face of the statue.

She searched the shadows, the Razor in her right hand and Chillrend gleaming in her left.

A ripple in the air, a suspicion of movement had her whirling around and she hissed as his blade sliced across her ribs, the poison and enchantments on it burning like she'd been branded. She struck out with the Razor, its needle sharp point punching through both his glove and his forearm before he batted her away again.

"Is that the best you can do?" Mercer had to shout over the sound of water.

Rath smiled, her teeth gleaming white against her brown skin. There he was, incapable of staying out of the limelight for more than a few moments.

She heard the clash of weapons below, as Karliah fended off the bewitched Brynjolf, and she didn't care. Indeed, she was glad Mercer saw fit to distract the Dunmer, and proud that she was the enemy he chose. This was right. He'd said it himself.

I knew it would end with one of us at the end of a blade.

There was nothing between them in style. They both fought without flourishes or feints, just fast, brutal strikes that wore down an enemy until they were open, and then followed up without mercy until they were broken.

She had youth and height, and he had strength and experience.

There was nowhere to run and nowhere to hide on the statue. They ducked and parried, mindful of the damp, slippery stone beneath their feet. They couldn't risk losing their footing, and so they both had to endure attacks they would have rather dodged entirely. Soon their armour and blades were bloodied, and their breathing was harsh.

This fight could not last long.

Mercer had such strength in him; she deflected, ducked, twisted, she could believe his fury and his Dwemer blade could shatter her weapons, and she knew it could cut through her armour like it wasn't there.

She brought the fury of a betrayed friend, the martial skill bred into the bones of every Redguard, and the blood-lust that was all her own and she hurled it against his defences, and he laughed at her.

But his laughter never reached his cold green eyes.

The wounds he'd inflicted on her arms and leg burned and her side was stiffening. She wished he'd just die already. The Razor had found his skin a dozen times, but Dagon stayed his hand. It would never be that easy.

"Rathleen! The water's rising!" Karliah shouted.

She didn't dare look. She swung Chillrend, the Razor in her other hand striking under the attack and she bared her teeth in glee as he moved too slow and she felt it slide into his side, grating between his ribs. She drove the dagger in right to the hilt, angling it upwards, seeking his heart, if he had one.

"Bitch!" He caught the glass blade on his dagger and Rath flung herself back, staggering, scrabbling for purchase as she yanked the Razor out of Mercer's ribs. She'd left herself unprotected and he was still standing, somehow. His sword came down on her neck.

Her left foot slid from underneath her and pain bloomed as her knee landed hard on the stone, but it saved her life as Mercer's poisoned blade missed her throat and sliced through her upper left arm, blood welling from the wound and flowing freely down her arm.

She expected another strike, an execution, as she forced herself to stand, forced her hand to keep holding the sword.

Mercer coughed and shuddered, swaying slightly. His teeth were stained red and he grimaced in pain as he inhaled.

Her eyes widened in surprise as he tossed his dagger aside. She heard it ring on the stone briefly before falling into the water and she raised the Razor defensively, unable to lift Chillrend any longer, wary of a trick. He too kept his sword pointed at her, and with his free hand he produced the Skeleton Key.

"Is this what you want?" he asked. "Or is it revenge you're after?" She risked a moment's glance away from his eyes to the Key and back. "Well, decide."

He flicked his wrist and the Key sailed into the air.

She didn't have time for conscious thought, let alone a rational decision. Rath turned to follow, bending her knees and leaping after the thin piece of metal as it arced out over the rising water. She didn't dare to look at Mercer, knowing if she lost sight of the Key in the murky water she'd never find it again.

She and the artefact hit the water at the same time. The surface was like a hammer to the chest, and Rath bit back a yelp of pain as her wounded arm was wrenched back. It barely seemed to respond to her commands and she sheathed the Razor and swum one handed, eyes open and fixed as the Key fell through the water ahead of her.

Her ears clicked and popped as they adjusted to the pressure, and then all she could hear was the water roaring endlessly as it fell from the ceiling to the surface somewhere above her.

Deeper. She forced the air out of her lungs, willing herself to sink faster, stroking with her one good arm. She remembered what she had learned in her youth diving in the river, competing with her brothers to see who might sit on the bottom the longest.

Oh, that she was in that sunlit water again.

The Key came to rest on an outcropping of rock, only an inch off falling to the floor below. She kicked harder, her hand outstretched, her chest aching with the deadly urge to draw breath. Just a bit further.

Her questing fingers closed around the Key, its jagged edges digging into her glove.

A skein of blood unwound in front of her eyes as she struggled to right herself, and start kicking upwards. She was numb in the cold water and had the idea she should be glad of it. Maybe she would just dissolve here, first her blood escaping, then her bones unknitting, her thoughts floating free, like bubbles.

What she'd thought was her vision darkening resolved itself into a shadow above her, a dark shape getting closer. She struck out for the surface, feeling her strength starting to ebb.

She opened her mouth to scream in pain as a hand clamped around her injured arm, and water rushed into her mouth and she choked, desperately fighting the urge to breath in. She looked up, and saw red hair, and she let Brynjolf pull her to the surface, trailing blood.

It seemed like an age before her head breached the surface. The water was now only a foot or so from the rocky ceiling. She tried to breathe, coughed, retched, and clung to Brynjolf's shoulders as she struggled to refill her lungs.

"Easy, Lass, easy." He trod water, holding her up.

"Where's," she gasped. "Karliah?"

A few moments later the Dunmer surfaced. "Do you have the Key?"

Rath could only nod, exhausted.

"Good. I've found a way out. Dive down and follow me."

The last thing she wanted to do was dive again, but dive she did. Brynjolf did most of the swimming, one arm around her chest, pulling her with him as she feebly tried to match his stroke. Rath was feeling light-headed and sick, and the other two Nightingales dragged her out of the water into the side passage. Rath lay on the cold stone, her short cropped hair plastered against her skull, her limbs aching with cold and her throat raw. She continued to shiver as Karliah lifted her head up and coaxed her into drinking some potions while Brynjolf held the wound in her arm closed. She'd have a scar to remind her of this day. She'd have several.

Rath recovered slowly, and eventually she ran her hand over her face, wiping the water out of her eyes.

"Back with us?" Brynjolf asked.

"I think so." She winced as she sat up. The potions might have knitted her back together, but she still hurt in dozens of places. She remembered how the battle had ended and her eyes widened. "Where's Mercer?" she asked.

"Down there, isn't he?" Brynjolf jerked a thumb at the water.

Rath shook her head. "He tossed the key. I had to choose. He's gone!" She bunched her hands into fists. "That bastard!"

"You made the right choice," Karliah said.

Rath wasn't so sure. "He was wounded. Maybe badly; I Razored him right up to the hilt, but-"

Like her, he was a survivor. She couldn't believe he was dead until she was standing over his cold corpse.

"We have the Key. That is what's most important,' Karliah insisted. "It must be returned to the Twilight Sepulcher."

"Hey, not so fast," Brynjolf said with a grin. "The Key's ours legitimately- well, it's yours Lass, if anyone's. Nocturnal wouldn't mind us using it for a while, surely. Just a few weeks."

"I can't see the harm, I suppose. Rathleen clearly needs rest anyway. The path within the Sepulcher is not straightforward."

Rath was barely listening to them. As she absently flexed her injured arm, she thought back to the fight with Mercer. She was so certain this would be the end. He fought like a man prepared to die, so why had he changed his mind? Why had he offered her the choice?

"I made the wrong decision," she said. "I should have killed him instead."

Brynjolf offered her his hand and she took it, letting the Nord haul her to her feet.

"Don't worry, Lass. Even if he did survive, he knows what kind of welcome he'll get if he shows himself anywhere in Skyrim." He sighed. "He's probably taken the guild gold and run for it. In two weeks time he'll be on a beach in Hammerfell or somewhere. I hope he drowns," he added cheerfully.

Rath knew Brynjolf was trying to cheer her up, and she managed a smile to thank him for his efforts, but she couldn't share his sentiments.

She didn't want Mercer to drown. He deserved better. He deserved nothing less than to die at the end of her blade, and she'd thought he'd understood that.

She tucked the Skeleton Key into her belt and cast one glance back at the pool of water before following her fellow Nightingales back out into the fresh air. When they emerged into the swirling snow hours later, Rath found no sign of footprints.