Peddler and Darkfriend
Padan Fain was a peddler who became a Darkfriend in his twenties for the promise of immortality. Continuing his work as a peddler, he came to Emond's Field every spring, and loved being the center of attention.
Dark One's Hound
Sometime in 996 NE he was chosen for a special task: to seek the Dragon Reborn. He journeyed to Shayol Ghul and met Ba'alzamon, who gave him dark powers to aid in his hunt. In 997 NE he journeyed back to Shayol Ghul and his mind was "distilled" of his findings. This process was agonizing, and fueled a resentment of Ba'alzamon and those he had been set to track. By 998 NE, given the special ability to track the ones he was seeking, he had narrowed his search to three boys from Emond's Field: Rand al'Thor, Matrim Cauthon and Perrin Aybara. With this certainty in mind, he brought Trollocs and Myrddraal to Emond's Field on Winternight.
After the failure of that attack, Fain fell out of favour with Ba'alzamon, and was forced to join the Trollocs in the hunt for Moiraine Damodred and company, running alongside the Trollocs until he passed out from exhaustion, and then dragged until he was able to run again. This continued until they reached the Taren River, where the Myrddraal sent him across the river alone before returning with the Trollocs to a Waygate. However, on the other side of the Taren he was captured by another Myrddraal before reaching Baerlon, with Fain forced to spend each night bent double in a Trolloc kettle.
When the Aes Sedai and her party hid in Shadar Logoth, he managed to escape the Myrddraal only to be trapped by Mordeth, the ancient spirit which had caused the downfall of Aridhol (the ancient name of Shadar Logoth). Mordeth had at last found the vessel he needed to command so he could escape the damned city; but because the Dark One had touched and changed Fain's soul, Mordeth could only merge with Fain, not overtake him.
The hatred of the Shadow felt by Mordeth combined corrosively with Fain's resentment of the changes forced upon him. After this merger, his compulsion to hunt Rand, Mat and Perrin grew even stronger, aided by the fact that he could already sense where they were. He blamed the boys, on some level, for causing what had happened to him. Following them along the Ways from Caemlyn to Fal Dara in Shienar, he was able to remove his ties to the Dark One and claimed to be a changed man; in fact, any changes wrought made him more dangerous and evil than ever (Myrddraal can make men sweat, but Fain makes Myrddraal sweat). In the chaos of the attack against Fal Dara, he escaped with the dagger Mat took from Shadar Logoth and the Horn of Valere.
While travelling in the Ways, Fain was caught by Machin Shin, the Black Wind of the Ways that devours souls, be they human or Shadowspawn. The screaming voices of the Wind greeted him as a friend and feared him, the Wind fleeing from him (this is the first time something living has been grasped by the wind and escaped). It is unknown whether this had any real effect on Fain, but the Wind appears to have picked up Fain's compulsion to hunt Rand; the Wind was next seen trying to force itself out of the Ways to devour Rand in Cairhien (again, a first, as it is assumed that the Wind cannot leave the Ways, and had never before sought specific people). It has since been shown that the Wind will be drawn to any Waygate that Rand attempts to open, effectively preventing Rand from using the Ways. Perrin does not have this problem, indicating that when Fain encountered the Wind his hunt for the Dragon Reborn had already been narrowed to Rand.
He enticed Rand, Mat, Perrin, Verin Sedai and Ingtar Shinowa to Seanchan-occupied Falme, where he lost the dagger and the Horn. Calling himself Ordeith (wormwood in the Old Tongue), he changed strategies from force to manipulation: convincing Lord Captain Commander Pedron Niall of the Whitecloaks, as well as Elaida do'Avriny a'Roihan, to oppose Rand. He also convinced Niall to send Whitecloaks to the Two Rivers, hoping it would draw Rand out. Unfortunately, he got Perrin instead, and the future Lord Goldeneyes of the Two Rivers broke him of his Whitecloak affiliations.
He is one of the most dangerous creatures in the known world, as dangerous as any Forsaken. He can corrupt people by just being in their presence; he can sense fear and tension and can tell a Darkfriend on sight. He has also developed a way to inflict pain by touch, from levels of 'merely' harmful to deadly. Eventually he recovered the dagger (his primary interest) in Tar Valon; he feels complete with it. He is very likely insane and is wanted by the Shadow. Slayer was sent to the Two Rivers to kill him, but failed miserably.
Padan Fain later entered into the service of a group of rebels outside Cairhien who opposed the Dragon Reborn, going by the name Jeraal Mordeth. He was recognized by Rand, but the attack of a bubble of evil prevented justice. Worse, Padan Fain used his dagger on Rand, slashing across the wound caused by Ishamael. Padan Fain escaped, and Rand would have died were it not for the presence of Aes Sedai nearby. He later appeared in Far Madding, where he killed three of the renegade Asha'man and lured Rand into a trap, hoping to finally kill him. He failed, however, and was forced to flee. Fain was not seen after the destruction of Shadar Logoth, but Robert Jordan confirmed that it had no effect on him.
He again appears in the prologue of Towers of Midnight where he is travelling through the blight, presumably towards Shayol Ghul. He slays a pack of Worms (a feat which a legion is apparently unable to accomplish) and then slays fist of Trollocs using mist and apparently 'zombifies' them, binding their corpses to his will. He has also taken to cutting his own hand with the ruby dagger. It is revealed that the mist which was previously thought to be a bubble of evil, was really due to Fain's influence on the world around him.