(A/N: Oneshot. Consider this a bridge between the end of the game and Advent Children.

Disclaimer: FFVII and its characters are owned by Square Enix. I own only these words.)

She drifted along, touching upon the lives and memories of those around her. So many souls, curling and dissolving among themselves. The warm green of the Lifestream encased her and she longed to let its embrace take her away, for her atoms to join the great current of life. But Aerith's will was strong. She held herself together a little longer, unwilling to let go of her memories.

The Planet had survived. Sephiroth had been defeated; she had felt his will snap. Though she had not expected Holy, once unleashed, to turn its fury upon humanity, still, her prayers had been answered. She called up the souls of the Planet and they prayed together and the Planet heard their call. Now the tendrils of Lifestream flowed back towards the earth. But she was curious. Where was Sephiroth? Had his corrupted soul been absorbed?

She began to search. The spirits she had awakened to join her in the fight were gradually settling back down. All around her, she felt only their relief and contentment. So she let the tide of the Lifestream carry her towards the Northern Crater, where the Planet's injury was still being healed. Not long ago, Sephiroth had nestled in that wound, gathering the energy to himself, keeping the Planet's wound open. While he grew stronger, the Planet bled.

A huge amount of energy swirled around the crater. Spinning endlessly, a constant gale surrounded it with light. Some of it had crystallised; a great web of Mako stretched across the roof of a cave. Further down, at the bottom of the crater, a pool of Mako churned, and little eddies broke off to run in rivulets wherever the earth cracked. She sailed into the very centre. There was something different here. She sensed anger, and in a certain place the Lifestream seemed to have stagnated. A dark mass had coalesced within the green flow. It struggled to keep itself separate from the Lifestream – even as she watched, stray tendrils tugged at the black mass and bits flew off. She would know that presence anywhere. The spirit who refused to be absorbed by the Planet. Sephiroth.

For a moment, a terrible memory flashed into her mind. The glint of a silver blade; the pain as it pierced her body; her eyes misting over. But death was not final. No, she thought. I have no need to be afraid of Sephiroth. This is my domain now. I am a Cetra and the Planet is with me. He needs my help.

"Sephiroth?" she said tentatively.

The darkness responded. It melded itself into an indistinct human shape. A face appeared, the brows drawn together and the lips curled back in a snarl. The presence loomed up beside her.

"You…"

"Sephiroth, it's okay," she said. "Let yourself be at peace now…"

She reached out and touched his shoulder. He hissed and recoiled; the semblance of skin had melted away. The Lifestream was corroding him, eating away like acid.

"No!"

His will was reforming. It fought the Lifestream, pushing barriers against it.

"Let go of your anger. The Planet forgives all, even you."

His eyes flashed. "My mother has a task for me. I will not fail her. I will not die!"

And then another voice whispered, a voice so chill and alien that it made Aerith's spirit shiver. She knew she had no control over this creature. It was not of the Planet.

"My son…" said the voice.

"Mother!"

"My son, come to me…"

Sephiroth stretched out a ghostly hand. His gaze slipped past her. Afraid, she shrank back and looked around her. But she couldn't see Jenova. Where was it? Had it infected the Lifestream? Desperately, she called the Lifestream to pool around Sephiroth. More and more gathered around him and it crashed against his barrier like water against rock.

"What are you doing?" Sephiroth demanded. "Stop it!"

"It's for your own good," Aerith said. "Join us, please. The Planet wants you to join us."

His form wavered. He was growing unsure. She willed him to give up, to let himself be absorbed at last. But Jenova's voice whispered in his mind, and Aerith was close enough to hear.

"You can live, my son. We only need another reunion. Come…"

"She's lying!" said Aerith. But now bubbles appeared in the Lifestream – dark, oily bubbles, with pictures reflected upon them. Memories.

"Remember how I held you?" Jenova crooned. "My son, my only son…"

"Mother…"

Sephiroth's eyes closed in bliss. His form began to solidify again; the long silver hair took shape and the black energy swirled with a hint of fabric flapping in the wind. Aerith saw the image in the largest bubble – a baby Sephiroth wrapped in his mother's arms, his expression one of pure happiness. She moved towards it, not sure what she was going to do – she had a vague idea that she could somehow pop it, but the darkness repelled her. She couldn't touch Sephiroth. Only words could reach him now.

"Sephiroth, she's not your mother."

His eyes flicked open. He stared at her through a film of oozing darkness and pale green Lifestream.

"You're a liar, Cetra, just like all your filthy kind. I remember my mother. I remember the way she held me."

Aerith shook her head helplessly. "Sephiroth… that never happened."

"I will take back this Planet for Mother." A manic gleam appeared in his eyes. "The Planet made a mistake saving humanity. So it falls to me to carry out the purge instead."

"Yes," Jenova whispered. "Make them pay – infect them… kill them…"

"You will all pay for the sins you have committed. You – the humans – this entire Planet is mine by right!"

"No!" said Aerith. "We can forgive you – you're only human-"

"I – am – not – human!" Sephiroth spat. And like a lock clicking into place, she sensed that his will was set. There was no saving him now. He was determined to return to the living world. She had to prevent him.

"Come," Jenova urged him.

Aerith threw her spirit against him and the entire Lifestream joined her, seeking to remove this impurity. And Sephiroth fought. This was a battle – a battle of wills. He threw memories at her: her death again, and mentally she heard him laugh at his triumph. Memories of the times Cloud had lost control and attacked her. The time he had finally broken his puppet and made Cloud give him the Black Materia.

"See," said Sephiroth. "See how my will always triumphs? I am stronger than anyone!"

No, you're not, Aerith thought. I felt it. I felt Cloud beat you. Can you handle my memories? Can you handle the memories of all the souls that have ever lived? I don't think so!

She sent him her own memories – times she had laughed with Cloud, joked with him, flirted with him. Girl talk with Tifa. Her first kiss with Zack. All the times she had fought with her friends and healed their wounds. And fragments of memories from all the other souls invaded his mind too. She submerged his ego under the lives of thousands. Under this assault, the great General Sephiroth was losing himself.

He tried to shut them out. He screamed his own name in his mind to remember himself. But the struggle was too much for him; he was having difficulty holding himself together. The green energy whipped the edges of his form away. Aerith urged it on – faster, faster!

Sephiroth's face was fading. "I – can't-"

For a moment, Aerith thought she had triumphed. Her spirit danced with joy.

"Come!" Jenova shrieked. The command seemed to split the Lifestream, flinging her away. The Lifestream plunged around her; she felt as though she had been dunked into a whirlpool. Black bubbles shot upwards.

"Mother-"

Aerith shook her head. The swirling around her had gone wild. Green and black energy fizzed, but the black energy was rapidly ascending towards the surface of the pool. She recovered her wits in time to see that Sephiroth had broken away – quite literally. Somehow, what remained of his damaged ego had latched on to Jenova and she had plucked him away. He had vanished.

The Lifestream settled again. It returned to healing its wound while Aerith looked into the world of the living. She didn't like what she saw.

At the bottom of the Northern Cave lay three unconscious young men. They were all silver-haired and dressed in black. There could be no doubt about it. Sephiroth's spirit – or what remained of it – had manifested itself once again. He was broken into three parts but she remembered Jenova's words. The reunion could make him whole.

"I'm sorry," Aerith murmured. She thought of Cloud and all her friends who were still alive and the suffering they had yet to face. "I did my best, but I couldn't stop him. Cloud, I hope you'll be ready one day. Ready to face him again."

Suddenly, she choked. The Lifestream was not wholly green again, as she had thought. A tiny coil of negative energy remained; it unfolded itself, the tendrils snaking out. She hadn't noticed, until it expanded.

The virus!

Slick as oil, the negative energy spread. It flowed apart from the Lifestream – and as she watched its progress, she realised with a sick feeling where it was headed – towards Midgar.

Jenova's voice cackled in her ear.

"Watch your precious children sicken and die, Cetra."

The presence faded. The virus had started its journey and she didn't know how to stop it. Aerith shook her head in dismay. So few cells… infecting so many. Well, she thought, it looks like I still have some work to do. The souls of the Planet depended on her. Her living friends depended on her. So she made a vow. Until the Planet had been cleansed, she would not allow herself to return to the Planet. She had to watch over Cloud and the others, and work out a way to help them. She was the last of the Ancients. She was the only one with the power to do it.

And when Sephiroth comes back, I'll welcome him with open arms. For that is the way of the Cetra.