Beautiful work, definitely. Might even make me have another round as the Kurios just to try a magic-based tactic.

You can see a real theme of getting more and more powerful with each step; I don't have to ask which is the adept, and which is the archmage. But the sudden transition in back is a bit artificial looking. MC's suggestion seems good. Alternatively, the front fades nicely; I doubt I'd notice it at all from a distance. Maybe you could have the entire area where the human and snake parts meet be that color, before (in the back, anyways) fading into the more colorful tone. If that made any sense whatsoever.
Of course, there are a lot of things that look way better in game then in previews; I had my doubts about the purple haired huntress, but in game, it looks perfect.
One last idiotically small note: what's up with the ears on the mage and archmage?
EDIT: Any plans for the Lamia race in terms of stat mods? Or will they be treated as non-specified race (e.g. human)?