Seiyuu
I do this with all of my fanfics too: I give them a voice cast.  Like, I pick an actor that I would like for the voice of each character.  And these are Japanese seiyuu, even though it's an English fic, because I'm more familiar with the Japanese actors.  I'm gonna get clips of them if I can soon, so you can actually hear how I want them to sound.

Aoife
Seiyuu: Tange Sakura
Previous Roles: Kinomoto Sakura (Card Captor Sakura)
Why: Aoife's a lot like Sakura (the character, that is), about the same age and all.  And Tange-san was using her natural voice in Card Captor Sakura so it shouldn't be too hard to play Aoife the same way.

Fawn
Seiyuu: Shiratori Yuri
Previous Roles: Kiryuu Nanami (Shoujo Kakumei Utena)
Why: Nanami is a stuck up brat.  Fawn is a stuck up brat.  -That's- why.  Also, they're the same in that they both have similar hairstyles and Nanami has three guys who follow her around and act as her servants all the time too, like Fawn. (and whenever I find out who their seiyuu is, that's who will play Steve, Bert, and Charlie)

Petra
Seiyuu: Sakamoto Chika
Previous Roles: Kou Yaten (Sailormoon), Nuriko (Fushigi Yuugi)
Why: She's played a few cross-dressing or gender-bending characters before, and I know I always cast her as all the cross-dressing or whatever characters in my fics, but it just sounds like her.  She can do both a male and a female voice, which she wouldn't really need for Petra, but she'd be used to it.  Petra's sort of based on Nuriko anyway.

Aidan
Seiyuu: Midorikawa Hikaru
Previous Roles: Ail and Fiore (Sailormoon), Zelgadis (Slayers), Tamahome (Fushigi Yuugi)
Why: I think Aidan is sort of a Zel-type person, don't you?  Okay, no, he's not that power-crazed (he's not power-crazed at all, in fact)... Guess Fiore's voice is more what I had in mind.

Sora
Seiyuu: Hayashibara Megumi
Previous Roles: Lina Inverse (Slayers), Himeko (SMS movie), onna-Ranma (Ranma 1/2), Ayanami Rei (Evangelion)
Why: Take a look at some of her past roles and then _you_ tell _me_ why. ^-^ I think Lina's voice about covers it, maybe softer though, especially for the emotional parts.

Ferio
Seiyuu: Mitsuishi Kotono
Previous Roles: Tsukino Usagi (Sailormoon), Katsuragi Misato (Evangelion), Arisugawa Juri (Utena)
Why: I know what you're thinking: "USAGI'S seiyuu for FERIO?!"  No, no, not the voice she used for Usagi.  I'm thinking along the lines of the voice she used for Juri, which was nearly the opposite.  Not to be saying anything bad about Juri, because I like her, but as Juri Mitsuishi Kotono could be the cold, seemingly emotionless bitchy type.  Perfect!

Ruari
Seiyuu: I...forgot her name. ^^;;
Previous Roles: Alielle (El Hazard)
Why: Oh wow, Alielle is so Ruari!  I love her, she's so cute!  And she even kinda looks like her.  Heck, they could be clones.  I'm CONVINCED that when they gave Ruari human DNA, they gave her Alielle's. ^-^ Now I just have to find out who Alielle's seiyuu is...

Bonnie
Seiyuu: Fukami Rika
Previous Roles: Aino Minako (Sailormoon)
Why: Minako acted a little like Bonnie in her pure heart episode, kind of crazy and desperate to prove herself.  Yeah, it's just one episode, but still it proves this seiyuu could do that for Bonnie's character.  Hey, this is weird...Usagi's seiyuu and Minako's seiyuu playing enemies.  Huh.

Clyde
Seiyuu: Miki Shinichirou
Previous Roles: Kojiro (Pocket Monsters), Yuuki Keisuke (Fushigi Yuugi), Allen (Tenkuu no Escaflowne)
Why: This is the seiyuu that played Kojiro (James) in Pocket Monsters, and since his and Clyde's personalities are similar, I think the voice fits.
 
Ermynne
Seiyuu:
Previous Roles:
Why: