Irkngthand was a sprawling mass of dwarven ruins sinking into a sea of snow. Bandits had claimed it with wooden bridges connecting the crumbling and collapsed towers. On the way up the mountain to the ruins, a freezing blizzard blinded them, greatly slowing their progress. Even though they could barely see three feet in front of them because of the harsh wind and snowflakes, Macayla, Brynjolf, and Karliah soon realized their cautious approach wasn't needed: each and every bandit had been slaughtered, their pools of blood striking against the white snow. Mercer.

"I hope we aren't too late," Karliah breathed as they headed up into the ruins, trying to find the entrance. After following the crisscrossing bridges, they found the golden double doors into the Irkngthand Arcanex.

They gratefully ducked out of the frigid weather and found more gruesome evidence of Mercer Frey's passing: more dead bandits, some gutted still in their bedrolls. Blood had never bothered Macayla—she had spilt enough to probably bathe the entire city of Markarth—but she hurried by with the others—bandits were notoriously cruel and ruthless, but they still didn't deserve to be butchered in their sleep.

As they crept through the crumbling ruins, they had to fight off some Dwemer automatons that had somehow slipped past Mercer—pieces of fellow guardians littered the path he took. Macayla noticed Karliah's head turning to admire a stone fountain or the sturdy dwarven architecture; she probably would've liked to stop and study it, but they couldn't be distracted.

They took a lift down further into the underground city and emerged onto a gated platform in a huge cavern. The platform overlooked the ground with golden-roofed towers and stone Dwemer structures. The extremely high ceiling was aglow with the mysterious glowing mushrooms known to grow underground; the ceiling looked like a craggy night sky with stars.

The Nightingales took just a moment to gape as they walked up to the golden bars, preventing them from falling off. Movement through the bars caught Macayla's eyes, and she looked down. A dark figure slinked up a set of steps; she recognized the arrogant walk.

"Look down there: it's Mercer," she whispered to the other two.

They moved closer to the bars to look. Brynjolf gave the bars a shake—they barely shuddered. "Damn it, we can't get through these."

"This way, then; hurry," Karliah called as she headed toward the next opening.

Mercer looked to have known he would be followed, for he left traps waiting to ensnare them; it only slowed them down some. They came onto a puzzle needing both lamps on either side of a door to be lit to raise the gate; they found two levers and after realizing there was a timer, Brynjolf and Macayla took a lever each and, pushing them down within seconds of each other, lowered the bars.

After winding hallways, another enormous chamber waited them. More crumbling structures littered it, but still standing stone bridges wound in the air to meet doorways. A problem was the Falmer skulking about—they resembled humans but were extremely pale, scrawny, hunched over, and blind. Being unable to see only increased their reliance on hearing, so even as quiet as the Nightingales could be, the slightest scrape of a boot would alert them.

So, Macayla and Karliah took charge of killing the creatures from afar with their bows; it would be hard for Brynjolf to sneak close enough to slit one's throat since he only fought with daggers. He trailed close behind them as they silently dwindled their number, watching for stragglers or survivors.

A booming sound of falling rocks suddenly sounded out; as the crashing stones struck the ground, the floor vibrated under their feet. They didn't know where the sound came from, but they hurriedly cleared a stone bridge in case it decided to fall. It took a while for the falling rocks to settle, and now they noticed clouds of dust blown into the air ahead of them.

They cautiously crept forward to find stone steps descended into an entrance but a crumbled tower to be blocking it.

"So, this is what we heard: the entire tower collapsed," Brynjolf said.

"The only reason to do that is to block pursuit. It must be Mercer." Karliah turned and considered a stone bridge winding up above them. "We'll have to find another way around; hurry." She began toward it.

"Mercer was able to knock this over? Gods..." Brynjolf said in disbelief.

"It's the Key, Brynjolf," she explained. "In his hands, there's no telling what he's capable of."

Brynjolf looked at her. "This isn't going to be as simple as I thought, lass."

Macayla took a deep breath. "No, but we can kill him."

They followed the bridge up to a door, went through and came onto another massive chamber crawling with Falmer. A Dwemer Centurion slept in its arch; Macayla spotted a button to awake it. She quietly explained her plan of having it attack the Falmer and they would kill what survived. She pressed it. The automaton awoke, and they stayed back as it attacked the Falmer swarming around it. The Centurion won and even if it was weakened, the three Nightingales gave it a wide berth as they snuck around to another door.

The next section was gloomier, less organized, and reeked of Falmer; Karliah said it had to be their hive. They were even more careful than before in sneaking through, going painstakingly slow as they crept around some Falmer. If a small number, they would kill them, but in one case there were so many, they would've quickly become overwhelmed; so, they snuck past them, even climbing up some dwarven pipes to pass overhead.

Water rushed through the pipes they tiptoed across; Macayla guessed they had to be under a lake now. Once they dropped down, they once again found evidence of Mercer with slaughtered Falmer and the gate to a Chaurus pen open; the enormous dead insect lay inside, and a tunnel burrowed into the rock wall. They followed the sloping tunnel downward until it surprisingly ended at a door.

"This has to be it," Karliah whispered.

Brynjolf rolled his shoulders. "I can't wait to get my hands around that bastard's neck."

Macayla looked at him; even though hard to see his eyes, they burned with hunger. "Because of what he did to Gallus and the Guild?"

He looked at her. "And to you."

She was touched that he felt the need to defend her by killing his current Guildmaster. Those three words meant that he did care for her.

"We must be ready," Karliah suddenly said, snapping Macayla back to attention.

"Right; what's the plan?"

"We'll see as soon as we get in."

Brynjolf gave her a final glance before he walked to the door; he carefully and silently pried it open; Macayla and Karliah slipped in, followed by him.

A gigantic statue of what the Falmer used to look like faced them: a Snow Elf. It sat cross-legged on the ground below the ledge they stood on; one hand held a staff, and the other held some sort of flat tablet—on it laid a bloody and dead Falmer. Propped on its face, Mercer Frey pried out a milky-white gem—the other Eye of the Falmer was gone.

"He hasn't seen us yet," Karliah whispered, her voice lost in the loud metallic scraping. "Maybe we can climb down the ledge and—"

Suddenly, the room shook, and the sanctuary groaned in protest. "Karliah," Mercer began when he pried out the jewel and dropped down to pick up the loose Eye. "When will you ever learn you can't get the drop on me?"

He slowly turned to face them with a smug, wicked smile. The ceiling broke apart and large boulders came raining down. Macayla dove to the side to avoid being squashed, but when it collided into the ledge, the ground gave way under her, and she went tumbling down into the crater at the statue's base.

She heard and felt something snap when she landed hard; Macayla pushed up to find her precious bow broken in two.

Mercer chuckling brought her eyes up; he now stood on the flat tablet the statue held. Some of the pipes hidden overhead burst and freezing water cascaded down.

"Why am I not surprised you survived the Jarrin poison?"

"I've been proven hard to kill."

His face grew hard. "That's clear. When Brynjolf brought you before me, I could feel a sudden shift in the wind. And at that moment, I knew it would end with one of us at the end of a blade."

"It's going to be you," she snarled as she threw down her broken bow and unsheathed Chillrend and her dagger. His eyes narrowed at the sight of his sword—she had switched out her sword for it, hoping to irritate him for showing she stole it. "Give me the Key, Mercer!"

"What's Karliah been filling your head with? Tales of thieves with honor? Oaths strife with falsehood and broken promises?" Water rose around her ankles as more rocks fell. "Nocturnal doesn't care about you, the Key, or anything having to do with the Guild."

Anger unfurled within her chest. "I don't believe you; Nocturnal guides me."

Mercer scoffed. "Then it appears the shadows shroud more than your presence—they blind you as well. When will you open your eyes and realize how little my actions differ from yours? Both of us lie, cheat, steal, and even kill to further our own ends."

Macayla glared at him.

"I recognized a killer back at Snow Veil Sanctum. The little noble thief isn't so righteous after all. There's not much difference between us."

"The difference is I still have honor."

"It's clear you'll never see the Skeleton Key as I do—as an instrument of limitless wealth. Instead, you've chosen to fall over your own foolish code."

"If anyone falls, it will be you."

Mercer sneered. "Then the die is cast and once again, my blade will taste Nightingale blood!"

Someone straining and rocks being shoved aside sounded above her. "Lass?" Brynjolf cried out frantically.

Mercer's head snapped up seeing him emerge. A red orb suddenly appeared in his hand, and he shot it at the ledge where Brynjolf and Karliah stood. Ringing metal sounded out as steel clashed against steel.

"What's going on? I can't control myself!" Brynjolf said.

"Karliah, I'll deal with you later, after I rid myself of your irksome companions."

"Damn you, Mercer!" Karliah yelled.

The Guildmaster turned back to Macayla below him, pulled out his sword and dagger, and jumped down; as he dropped though, he became invisible.

Macayla stared in shock. "You coward!"

She could see where he landed from the sudden explosion of water. As he ran toward her, his feet splashed the water—she would have to keep her eyes glued on the water to see where he went.

The splashes got close to her, and she swung upward to deflect his sword coming down. He still has a dagger. Macayla stabbed her dagger straight in hopes of him using his to parry hers. Sparks flew as the metals scraped against each other.

She felt his sword moving up to slash her, and she twirled away from him; as she turned, she swung her sword at where his head should be. He likely ducked under it and she followed the splashes to her right. Macayla shot forward with her sword out to impale him; he caught her extended arm and threw her into the ledge's wall.

Her head and back banged against it; instincts made her duck away to miss his attack. Sparks flew off the rocks as his sword slashed down. As she slipped by him, a sharp pain slashed across her arm from his dagger.

She kicked back at him, hoping the water would reveal his invisible form. It did, for only a moment, long enough to see him lunging at her. Macayla deflected his thrust then wildly swiped at him; blood sputtered out of thin air, following the direction of her dagger.

Mercer hissed before a kick to her chest threw her backwards. Her dagger flew out of her hand as she landed back in a splash of water. She didn't have time to search for it; she rolled to her right to avoid a downward killing stroke.

Macayla hissed as Mercer swiped at her, cutting a thin but thankfully shallow slice into her back. A sudden spin had Chillrend chopping into his arm; he yelled in pain as he recoiled back, and his sword was revealed as it fell from his numb hand. She could pinpoint where he stood now by the gushing blood and the ice-enchantment on Chillrend freezing the wound and icy fog rising from it.

Somehow, he knocked Chillrend out of her hand by painfully slashing his dagger across her hand. The hardened leather protected her hand, but her fingers were still nicked.

Instinct made her duck again under his wild swipe, grabbed the steel dagger Brynjolf had stolen for her, then drove it into Mercer's gut. He gurgled and, in a flash, he was visible in front of her. His chest and left arm were slick with his blood, and a small line began to drip out of his mouth.

"I told you I would kill you," Macayla said as she moved the dagger even deeper. He choked in pain again and tried to bring his dagger up to cut her. She easily knocked it out of his hand quickly losing strength.

A sudden power swelled inside of her, and it quickly swept over her soul—something overcame her, taking her place; she wasn't herself anymore. She felt like she had grown three times her height. The hand she had used to knock away Mercer's dagger grabbed the side of his face.

"You can't run from me." Her lips moved and her chest rumbled, but it didn't sound like her own voice.

His eyes grew round, and he blanched. "You're... her?"

A separate part of her pulled the life out of him; soon Mercer's eyes were just blank and dull black orbs and he crumpled lifelessly.

Macayla suddenly felt weak. She started to fall herself but the energy returning to her revived her and kept her standing. She somehow felt whole again.

The surrounding sanctuary continued to rumble as pieces of the ceiling fell. Now she realized that the water level that had been around her ankles almost reached her waist. Quite a few waterfalls had sprung up since her fight with Mercer started, but past the rushing water, she couldn't hear the clashing blades of Brynjolf and Karliah.

"Macayla! Macayla!" Brynjolf yelled; in seconds, he was visible on the top of the ledge and looking for her. "Are you alright?"

"I'm fine; are you and Karliah—"

The Dunmer suddenly appeared beside him, unhurt. "We're fine, but everything's coming down quick; grab the Skeleton Key and the Eyes! We'll get the door!" She turned and headed back for the exit; Brynjolf quickly disappeared, too.

Macayla turned back, searched for Mercer's semi-floating body, and searched for the three items. The Eyes were as big as a man's head but surprisingly light; she stored them in her satchel, then found the Skeleton Key.

The rounded end was blue, and it had multiple prongs on the other end. With it in her hand, she felt a strange power awakening within her.

"We can't get this door open; it's barred from the other side!" Karliah said.

A loud thud sounded, followed by another, as Brynjolf threw his shoulder against it. "Rocks must be blocking it!"

Macayla straightened. "Maybe I can open it with the Key!" She remembered Chillrend, moved over to where it fell, and dropped down into the water to grope for it. Her hands wrapped around the hilt, and she stood again; she sheathed it as she headed for the ledge wall to climb up.

"It won't work that way," Karliah said. "A door's got to be able to open to be opened. This one is blocked."

Brynjolf helped haul her up on the ledge. "Well, maybe I can blast it open or something, like with the power Mercer had. How does it work?"

"You have to have time with it to learn what it can pull out of you."

The meaning of her words hit them hard. "So, we're trapped?"

"No," Brynjolf said. "We're not dying in here; there's got to be another way out."

They dispersed to frantically search the walls for another exit. The center crater filled up and now the water rose where they were on the ledge surrounding the statue. More rocks tumbled from the ceiling, opening up another waterfall of the freezing water. The water level rose faster.

"I can't find one!" Karliah's voice pitched in her panic.

Macayla glanced down at the Skeleton Key in her hand. The water now swirled around her calves. "Well, with it submerged with us, no one can abuse it like Mercer." Her voice was quiet but deadpanned; she had already accepted their fate.

No one said anything. "Lass, I'm not letting you drown," Brynjolf said.

Her hand closed around the Key, and she looked at him. "I'm not afraid."

She felt his eyes heavy on her; Karliah didn't say anything, acknowledging that she had no way of escaping death this time. Brynjolf suddenly sloshed through the rising water toward her, set on something, but as he reached out to grab her, the ceiling shook a final time and multiple boulders fell, merging the individual waterfalls into a giant one.

The lake they were under filled the sanctuary in seconds. The powerful currents separated them; the force under the waterfall was so strong they couldn't swim into it and out through the hole. Brynjolf and Karliah swam back toward her so they could die together.

Macayla heard another groan and the shifting of rocks; with it muffled by the water, she couldn't tell where it came from. She saw Brynjolf's head turn, then he frantically waved at the two women to point at an opening where a wall met the ceiling—light shone through the water. They swam toward it, not sure if the exit might be closed off by falling rocks.

Only one could swim through the narrow hole at a time. Macayla gulped in the precious air when she broke through the surface; she heard Brynjolf do the same behind her. In front of her, Karliah had reached where the water grew shallower and trudged up the slight incline in a cave.

Macayla followed her and almost ducked back down into the water—the blizzard had stopped, but strong, frigid gusts still soared through the cave's entrance. She stopped beside Karliah, shivering; the small Dunmer in the same condition.

"We need to see... where we are," Brynjolf said, his voice not as strong but chattering.

They peered out of the entrance to find them on the edge of a frozen Lake Yorgim. Since the blizzard was gone, they were able to spot a cloud of smoke lazily rising into the bleak sky. The Nightingales focused on skirting the thick ice and hoped to find a fire.