Okay, I've been thinking about this for a long time, and here are a few casting choices I've liked:
Castellan Lebbick: Patrick Stewart. Or, if he ends up playing Joyse, Patrick O'Quinn.
Havelock: Peter O'Toole (if we can get this filmed before he dies)
(On that note, I wanted Richard Harris as Joyce, but we can't have that now. Sad.)
Terisa: I always had a young Daryl Hannah in mind, but lately I'm liking Nicole Kidman. She doesn't have to be that young, does she?
Master Eremis: He's gotta be tall and kinda goofy looking, but also have some charisma. Jeff Goldblum. Otherwise, Clancy Brown, who doesn't bring the goofy, but brings a lot more of the menacing danger.
Darsint: Vin Diesel, of course.
Prince Kragen: This one's new. I had always seen him as Timothy Dalton, based on the similarities between this character and the Prince he played in The Lion In Winter. Too old now, plus there's someone better who matched him physically.
Naveen Andrews, the man who plays Sayid in the series "Lost".
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I still can't really picture Myste or Elega.
The Domne should be Liam Neeson.
The Perdon: Sean Connery? Why not?
Vagel: Patrick Bauchau
Gart: Ray Park, although this may be a cliche at this point. Sorta like casting Patrick Stewart in anything.
Finally, the most important one:
Geraden must be played by Nick Stahl. Anyone who watched Carnivale would see it. He basically played Geraden for a great part of that series. Someone who has incredible power, but forces around him are conspiring to keep him from realising it. Then, when he realises how much power he really has, his entire demeanour changes. He'd be perfect, imo.
More as I think of them.