Selakiir

Trope: The turncoat. The turncoat is a character who switches sides, from good to bad, during a pivotal moment - and can often end up being the deciding factor for which side wins, bringing with him a wealth of knowledge, information from his previous side, and useful skills that his new side previously did not have, along with some interesting ethics and practices that his new side never would have thought to use. I see Selakiir as a sort of veteran assassin who has worked for the "bad" or "evil" side ever since his younger, teenage years, brought up in assassin life. Due to such, he would possess a wealth of unique and developed abilities and knowledge that most other assassins do not have - and he is one of the most infamous ones alive (well, still alive, as most do not live as long as he does, but nobody has been skilled enough to kill him yet). Yet, throughout all his years of working for evil, he has always known that it would never win - they just paid better than the good. However, at one point there would be a huge plot where it dawns on Selakiir than evil will win this time if he doesn't intervene - and so he switches sides, probably killing the man who hired him and bringing all of the information for the evil's plans to the good side. He'd be seen as a turncoat, as untrustworthy and with shady ethics, but he would stay true to his own ethics in the end - to offer his skills for payment, but not to tip the scales so far into evil that evil wins. After all, he just wants to get paid - not see the world go to crap.