Asmodean
Asmodean (ahs-MOH-dee-an) is a major antagonist in the Wheel of Time fantasy series by Robert Jordan. He is one of the Forsaken and likely named after the demon Asmodeus.
Background
A Forsaken of no great significance, his real name is Joar Addam Nesossin. A musician and composer during the Age of Legends, he swore fealty to the Dark One so that he could spend eternity perfecting his craft, and he used his dark powers to destroy his rivals. As a sign of his loyalty to the Dark One, Asmodean destroyed a museum of art and all the people within it when he became a Darkfriend. Asmodean was also remembered, with some bitter hatred, for the execution of his mother, who also was Aes Sedai. This is a rare occurrence that even in the Modern World of the Wheel was remarked when Emond's Field was visited and three generations of women were found to be linked by the ability to channel Saidar. It is known that he first severed his mother from the One Power before giving orders to Myrddraal to execute her. In The Fires of Heaven there is mention of her screams.
In The Series
Asmodean battled Rand in Rhuidean, and lost when Rand severed his link to the Dark One. leaving him exposed to the taint on Saidin. Lanfear then shielded Asmodean so that he could only channel "a trickle", and instructed him to train Rand in the Power (ironically, Asmodean's attempt on Rand's life at Rhuidean eventually kept Rand from being killed by ignorance of the Power). Asmodean was known among the Forsaken for his habit of oft-traitorously throwing his lot in with whomever he thought would win, which perhaps explains why the Forsaken did not attempt to rescue him. Disguised as a gleeman named Jasin Natael, he trained Rand diligently and without signs of treachery, and as time passed it seemed as if he might genuinely want to join the side of the Light.
While crossing over the Spine of the World near Kinslayer's dagger, Asmodean lamented about his home city of Shorelle as they passed a decaying ship in the high passes of the mountain pass. Because he was sealed in the Bore before the Breaking of the World, it is believed that Asmodean has no known knowledge of precisely where Shorelle would have been located.
He was assassinated suddenly in Caemlyn after he came with Rand to help defeat Rahvin. He was also 'killed' earlier during the attack on Caemlyn along with Mat and Aviendha but this death was undone when Rand killed Rahvin with balefire. Although some Forsaken are reincarnated with different names, it is unlikely that Asmodean will ever return, since the Dark One told Demandred that Asmodean, along with Rahvin, "died the final death." It appears to be a constant in the series that if an individual is killed with balefire, the Dark One cannot reincarnate them as their thread has been burned out of the Pattern.
The 'Whodunnit'
The identity of Asmodean's killer has puzzled readers since the fifth book was published; few were able to assign it conclusively to one of the characters. Lanfear, the only character suspected to have both means and motive, has the airtight alibi of having been dead at the time (Lanfear has since returned from the grave as the individual known as Cyndane, but neither version was alive at the time of Asmodean's death). Other theories involved fellow Forsaken Graendal and Sammael, who have no known motive but similar means. Finally, some believe that Slayer, acting as the assassin of the Forsaken, killed him.
In interviews, author Robert Jordan insisted the identity of the killer should be "intuitively obvious," and has steadfastly refused to make any definitive statements on the matter, especially since at least one reader (he says) has come up with the correct answer. However, he has stated that he will include the information in the series' final novel, A Memory of Light if he can find a way to do so, and if not, he will announce the killer's identity after the novel is released in paperback.
Until then, the clues we have with which to puzzle this mystery out are:
1) The Dark One says that he has "died the final death" most likely meaning balefire. This is important because it narrows the suspect list to those who know the weave of balefire. These are: Moiraine, Any of the forsaken (except Ishamael, Lanfear, Rahvin, Aginor, Be'lal, and Balthamel who are all dead), and Rand, possibly "under the influence" of Lews Therin. The latter is unlikely, because Lews Therin Telamon has not yet before taken control of Saidin completely, and Rand thinks that he would take care of Asmodean himself if showed up. It seems clear that Rand does not even know if Asmodean is dead as of Lord of Chaos.
2) The killer also must know the whereabouts of Asmodean, and because we have reason to believe that only Lanfear out of all of the forsaken knew about the plot, none of them could have killed him without a little compulsion to get the information out of her (and that's Graendal's specialty).
3) The killer needs motive. This could be any of the Forsaken not wanting Rand to grow stronger and defeat them. Moiraine did know "Jasin Natael"'s real identity, as referenced by her final letter to Rand, and may have continued her quest of balefiring every Forsaken she finds, but she, like Lanfear, was also out of the action, imprisoned with the Aelfinn and Eelfinn in the silver tower. Rand also may have wanted to dispose of him, because after unraveling his shield, Asmodean was a threat if he tried to overpower him, and Rand eliminates threats as quickly as possible, as we have seen.
4) Asmodean's death is described simply as "death took him." It is known that Moridin (a.k.a Ishamael) means death, and may be a simple reference that Ishmael may be the killer.
A 12 December 2000 interview at CNN.com is frequently pointed to as proof that Graendal killed Asmodean, though Jordan (once again) refuses to confirm or deny the allegation.
Trivia
The name Asmodean, like most names in the Wheel of Time, seems influenced by mythology. Most obviously, it can refer to the Biblical demon Asmodeus. Unlike many, Asmodean does not directly tie to his namesake, acting as neither tempter, nor inducing any gambling. One might draw connections to the myth of Asmodeus marrying Lillith as analogous to Asmodean entering a pact with Lanfear, but that is sketchy at best. A clearer parallel might however be proposed between the story of Asmodai being trapped into aiding and teaching Solomon, and Asmodean being trapped into aiding and teaching Rand.
It is interesting to note that Asmodean, while being completely useless to the Shadow, was almost single-handedly responsible for the survival of Rand, the Champion of the Light. After turning to the Shadow and being remembered for an Age as one of the worst human beings ever known, Asmodean indirectly saved the world.