Who is Padan Fain from Lord of Chaos and what is their importance?

Padan Fain was once a peddler and merchant to the Two Rivers. He later turned Darkfriend, and sometime after that, he fell sway to an even more ancient evil, at Shadar Logoth. Padan is described as unpredictable, and he clearly wishes Rand were dead, but his alliances to the Dark One is less clear.