Hmmm... at first seeing the whole 300 years old bit, I was a little reluctant to allow this, considering I didn't offer this initially, but then again, each character has to be unique somehow. Instead of a Paladin/Assassin, you're part of the Dark Circle, a group of paladins who turned from their prayers to the gods and used their skills to kill mercilessly instead. The Darkness had seen this blatant opposition to the Spectrum and decided to "bless" these paladins with eternal youth, the cost was grave;however, as the few members of the Dark Circle would not ever make contact with the gods again. Which means... you don't have a color. So...
Edit a couple things.
1: Change your profession to just assassin, as you're not a paladin anymore.
2: Set an age, if nothing else, set how many years it's been since you received eternal youth from the Darkness.
3: Put (none) for your color.
I think we can roll with this, although there has to be some explanation for why a 300 year old guy's skills are comparable to those of the 7 other adventurers.... but maybe that'll work itself out along the way.