I've read a few forum posts about the desire for there to be more playability for 'evil' characters, but I think it's worth considering how characters like this (and evil npcs) should be designed.
For, me too many evil characters in RPGs fall into a limited number of easily recognisable categories, some of which are rather tired and stereotyped:
Firstly, characters who loudly identify themselves with the forces of 'evil'. E.G - T'anarii and Baatezu from Planescape, worshippers of evil gods, or whole races (Drow, for example) who essentially walk around proclaiming 'I am evil' with their every word and deed.
Secondly, characters who are consciously amoral, motivated by greed or lust for power, and who again openly revel in their own perfidy. Edwin from Baldur's Gate would be a good example.
Thirdly, outright sociopathic characters, who will happily kill, butcher and steal without any underlying morality or motivation.
While each of these evil 'types' has its place, I would like to see some more nuanced 'evil' characters, with different and more complex motivations and character traits.
Some thoughts:
Many evil characters are not aware that they are evil, and would perhaps even characterise themselves or their actions as 'good' or at least 'necessary'. To use a historical example, many Nazis would fall into this category - committing evil actions whilst somehow believing that they are acting for the greater good.
Evil characters are just as capable of falling in love or developing deep and lasting friendships as any other character - not all of their relationships have to be based on cynicism and self advancement.
There are limits to 'evil'. An evil character might not have problem murdering a totally innocent adult man for profit or even for fun, but might balk at harming women and children. The same character might have no problem killing for pay, but might consider a religiously motivated human sacrifice to be an abomination.
Evil characters can be redeemable. It's interesting that a lot of RPGs have a mechanism whereby the player character's alignment can change, but very few (correct me if I'm wrong), have a way to change the alignment of NPCs. There are a number of perfectly feasible and realistic ways by which the alignment of an evil character could shift - religious conversion, falling in love for the first time, spending a lot of time with a powerful and charismatic 'good' character, a bout of introspective depression, or even brain damage from one too many knocks on the head. It would be very satisfying for a 'good' player character to gradually, perhaps over the course of a whole game 'convert' an evil character to their way of thinking (or visa versa - an evil PC causing a good character to 'fall').
I sincerely hope that Project Eternity has some well thought out, complex and nuanced 'evil characters', rather than a few cardboard cut-outs with a penchant for killing and a maniacal laugh...