They were back at Morgana's hovel and Merlin's words still rang in her ears.
Emrys will be their doom.
It made her stomach twist and turn. Was the Cailleach wrong or was Merlin faking the whole thing? He flinched when he saw the chains hanging from the ceiling and he unconsciously felt his wrists. The first thing Morgana did was remove them and hid them behind the chest in which she kept her tools, tools not meant for torture.

Meanwhile Merlin wasn't that much at ease either. He had been tortured here, twice, and everything in sight was a constant reminder of it. The warlock told himself to get over it, however difficult that might be. What was far more important was finding a way of striking Arthur and Camelot so she could sit on the throne. It wasn't an unpleasant thought to see her back on the throne but it would take more than a bit of effort.

Morgana's original plan with Sir Ucron had been perfect but not anymore, certainly not for Merlin who wanted to see the King suffer. Arthur would be far more careful in his selection of future knights. A new plan had to be thought up during which Morgana revealed Agravaine's allegiance. Merlin wasn't surprised, he had been on to him for a while. At some point Morgana dared to show him the artefact her sister had left her and Merlin pulled out his book of magic.

It was a coin of necromancy, to resurrect someone to serve as a shade. Tossed into a gateway between worlds, usually waters in which too much blood had been spilled. Gaius' history lessons served Morgana well as she knew of such a place, the Pool of Nemhain.

Merlin was new to all the plotting and scheming but with a few pointers came up with the most brilliant of plans. The sheer cruelty of his plan convinced Morgana that Merlin was dead set on making Arthur miserable. It was a bit scary to see him pick it up so quickly but maybe even Merlin had let his dark side wander in his dreams every now and then. She should have convinced Merlin to join her long ago. The plan did not only take into account the king's faithful knight but were actually part of the plan. With all the time he had spent with them, Merlin knew them inside out; hopes, dreams and weaknesses. That left Gaius and Gwen. Gaius had magic but out of practice and Merlin wouldn't hesitate to kill him if he got in their way. "Merlin, You can't tell her about your magic!" Perhaps things might not have turned out so bad if he had told her from the very beginning.

Their journey to the Pool of Nemhain was surprisingly silent as Merlin was reading a book, one of hers, save for the few questions she asked him. Near the end Merlin folded the corner of page and put it away, smiling. Morgana wondered what it was he had been looking for but discarded the thought when the dark waters were in sight. They dismounted and she passed the reigns to Merlin without thought. A bit shocked she looked back at the warlock believing it must've angered him to be treated like a servant, but he gave her a lopsided smile thinking she was being rather cute while he tied the horses to a tree. He followed her into the water until they were up to their waist in the lake. Hesitantly she threw the coin into the water hoping that she wouldn't be casting away her sister's final gift in vain. Bubbles came to the surface and from the waters rose Lancelot, just like Merlin remembered.
"My lady, my lord, my name is Lancelot and I am yours to command."

"He was once so mighty and now he's nothing but a shade." Morgana mused as Lancelot lay on the bed, sleeping.
"Death stripped him of his memories, his personality and everything else that made him Lancelot." Merlin spoke light-heartedly considering they were friends. Morgana turned around to reply and saw the warlock concocting a potion. Seeing as Merlin and potions didn't get along in the time of the druid boy, Morgana got up and looked over his shoulder.
Memory Potion was all the page said.
"You want to return his memories?" She asked. Merlin put his hand on the flask and shook it while he answered her.
"Not exactly" He took his hand off the flask and drank it in a single go.
"What the hell are you doing?" Morgana exclaimed not knowing Merlin had practiced a lot since the day he poisoned her.
"It'll help me focus." He replied as he sat down on the bed and put his hands on either side of Lancelot's head. Morgana saw his eyes glow gold just before he closed them and Lancelot's opened. The knight's eyes seemed to be glowing and upon looking closer she saw people and places move inside them, like a small vision. All three of them gasped, one setting off the other, as Merlin opened his eyes and Lancelot sat upright.
"Who is Gwen?" Merlin asked the shade.
"Lady Morgana's maid." Lancelot replied looking at the witch behind him. The shade's tone of voice betrayed he still didn't have much personality but the living Lancelot's personality was shaped by a life Merlin had no knowledge of. Merlin had given him the memories he required and kept everything else from him, that was what the potion was for, Lancelot would just have to fake the rest.

All that remained was a believable story for Lancelot's return to Camelot and then all the pieces would be moved into place.

AN:

Bringing back Lancelot might feel a bit cheap but it's not Lancelot du Lac, Merlin has far greater plans with him.
Reading all the reactions on a dark Merlin, I've gotten some ideas for a full-length story in which Merlin becomes truly evil, even cruel at times. Does that sound good?