Louise Cooper is a very accomplished fantasy author with several series behind her. I've read a few of her books, though by no means all. There was a seven book series (of which I've read the first 3 - couldn't get hold of the others) which was based on a tale rather like Pandora's box. The lead character was made immortal and given the task of hunting down and destroying the powers she had released. Titles... well I remember Nemesis, Nocturne and Troika, oh yes and Infanta, but I don't remember the rest.
There was also a series based around chaos and order. The Initiate, The Novice and The Master. I seem to remember enjoying these as well, but it's been a long time since I read them.