Authors Note:
This is what I think would happen if Atlantis was sentient. So basically the city slowed down this one persons ageing and she's been alive for over ten thousand years. This is what happened while she was sleeping.
Disclaimer:
I own nothing. Seriously I own nothing.
Guardian
She had been sleeping for seven thousand years, kept safe by the city as she protected it. She did not stir until they arrived, she once again had people to protect. She could have gone with the others when they fled from the war, but she had sworn long before that she would protect those who dwelled in the city for as long as she was able, and so she stayed.
She woke knowing power was limited. She rose the city so it stood on the waves once more. She waited until they needed her, but they did not so once more she slept. They angered the wraith and brought them back. She held back the ships and let them escape before sinking the city again.
She slept again until still more came. She rose the city and stayed hidden. In the end they destroyed themselves with a deadly nano virus they had created. She could not help them, and oh how she had tried. She sank the city and slept again. Each life weighed heavily on her as she slept hidden away from those she knew would come. They always did.
Sure enough more came. She rose the city but sank it a month later. They had also managed to destroy themselves. She tried to save them but their own arrogance destroyed them, and she could not stop it. She sank the city and slept again. The losses hurting her more than she admitted.
Finally another group came. They came through but she did not wake right away. She woke just in time to raise the city before it flooded. They went through the gate and brought back others they had saved from the wraith. "These are different from the others." She thought as she watched from her hiding place.
She watched them go through the gate and help other peoples. The wraith did come for them as she knew they would. But they did not flee like the others, they stood and fought instead. She helped where she could, killing as many wraith as she came across. She sealed wraith into parts of the city that were uninhabited and flooded them. She killed many hand to hand and shot a lot with their own weapons. She stayed hidden during it all.
When the ZPM arrived she protected its carrier until the shield was up. She protected them from the radiation when the nuclear device exploded, and hid herself again as the danger had passed.
She watched and helped quietly as they averted one disaster after another. She helped here she could, but always stayed hidden.
Finally they discovered her existence in the Ancient database, and she revealed herself. She was finally able to protect them properly, and she would until her death.