Beneath the Shadows: Collaborative RP Idea

Well, I'm wanting to do a fantasy RP. I have my first post written out, but the main plot and story line are yet to be created. If you're interested, please comment or mail me :) Thanks!
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Here is a short intro (aka my 1st post), followed by some need-to-knows about what I do/don't have in mind:
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It was a dark and eerie night, illuminated solely by the distorted light of the year's first eclipse. A heavy mist that blinded the eyes and hindered the senses rolled along the landscape of the hidden valley of Ishanari. Here, was where the lines of reality blurred, connecting the human and spirit worlds together.

Within the mist traveled a young half-demon girl who went by the name of Amaya. It'd been quite a while since she'd last traveled to the human world. She only hoped her human friends were alright. How long had she been away? Three years? Five maybe?

She smiled at the thought of how they'd react at her sudden appearance. How should she surprise them? They wouldn't have forgotten about her... Right?

Amaya was forced out of her thoughts as she felt a pull from one of the tendrils of mist that had wrapped around her arm. In this place, a loss of concentration and stray thoughts could lead to death. She again focused on getting through the mist, and it released her as she continued to move forward.

Soon she could make out the shadowy figures of other demons and half-demons wading through the mist. She held her hands out, "Akabara." A sword with a blood red blade forming in her grasp like a mirage. She held the sword close to herself, but ready to be used if one of the figures should attack or turn out to be a foe.

Before long, the mist thinned until she found herself standing at the edge of a small forest, the night air suddenly clear under the light of the eclipse. Glancing around she sensed no danger. "Release." The sword disappeared in the same mirage like fashion in which it had materialized.
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-Need-to-Knows:

1)I have not decided if this should be a historical or modern RP, so thoughts and opinions on the matter are welcomed.
2)The eclipse is important, but I'm not sure why yet, so ideas and suggestions welcomed.
3)In this RP, demons and half-demons have traveled to the human world. There can/will be relationships of friendship, love, hate, etc. between all three species (human/demon/half-demon), so we need characters of all three species unless this turns into a 1x1, which it might, though there must be a limited number of half-demons.
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My usual rules and expectations for RP partners:

1) No godmodding
2) No Mary Sues/Gary Stues
3) Must write 5+ sentences for each post
4) Outside of character speech, use good grammar
5) If romance gets graphic, take it to PM
6) Cursing is okay as long as it isn't in every sentence/post
7) Violence is expected, and it's fine to be graphic, but don't get TOO graphic
8) Unless worked out between players OC or IC, I have the final say in things such as who dies in a battle, etc. or whatever
9) Respect other players
10) Post regularly (every two or three days at most. Notify me if you'll be gone longer)
11) I can kill you off if you don't follow the simple rules above :)
12) Be creative!