In The Shadow Rising, we were introduced to the Slayer... a man that roamed the Wolf Dream and Tel'aran'rhiod, stalking Perrin and killing the wolves that lurked there. Who was/is this strange man? Well, as revealed later in the book, the Slayer was masquerading as Lord Luc... but who was Lord Luc? Allow me to explain.
In the years before the disappearance of Tigraine Damodred, her brother, Luc, disappeared into the Aiel Waste. He was never seen or heard from again. He was never annointed First Prince of the Sword, as was custom for the Daughter-Heir's brother. (This was, as most people of the Land believed, the reason that Tigraine herself disappeared years later.) No one knows what happened to him. However, when Tigraine's Aiel "husband" went into the waste to fight Trollocs and virtually commit suicide after her death, he was killed (run through) by a man that looked like Tigraine...
Similarly, years before in the kingdom of Malkier, Breyan Mandragoran-- grief-stricken and mourning her husband's death--plotted with Cowin Gemallin (also called Cowin Tairheart) to help her avenge her husband and seize the throne of Malkier for her son, Isam. When their deception was unmasked (and Cowin revealed to be a Darkfriend), Breyan and her son fled the city, only to be taken by the Trollocs during their flight. Their final fate is unknown, but it is assumed that they did not survive.
Now, what I find interesting is that these two men, while sharing the common trait of being lost in the Waste, have almost nothing else in common. They come from different regions. Different families (albiet both of them royal). We know that Isam could have had leanings toward the Dark One, but that's only through association from his mother and Cowin. But could Lord Luc, the son of the Queen of Andor, had any "evil" tendancies? We may never know.
However, they have one very remote and overlooked link: The Dark Prophecy. Although written primarily about Lanfear, Daughter of the Night, both Luc and Isam are mentioned by name in its text...
Luc came to the Mountains of Dhoom.
Isam waited in the high passes.
The hunt is now begun. The Shadow's hounds now course, and kill.
One did live, and one did die, but both are.
The Time of Change has come.
Blood feeds blood.
Blood calls blood.
Blood is, and blood was, and blood shall ever be.
What could this mean? If taken literally, one of these two men did die in the Waste, and one lived. But... somehow, they both now live, in the same body. (Think of how Rand al'Thor and Lews Therin Telamon are joined now.) Which is which? Well, we've seen Lord Luc roaming the Land. Does this mean that when he sleeps, Isam lurks within Tel'aran'rhiod? Can they change at will, no matter the time or place, or are they linked, one to live here in body, the other to roam in spirit? Furthermore, what is their purpose, and what does the Dark One intend to do with them? Could he be a new Dreadlord???
It would seem, after reading Winter’s Heart, that I was correct. Isam lurks in Tel’aran’rhiod, while Lord Luc roams the Land. (It was also revealed the he/they killed that Gray Man in the Tower way back when...) Here is the relevant info from the text of Winter’s Heart...:
[WH: 22, Out of Thin Air, 447-8]
Isam paced the room, studying by the ever-present light of Tel’aran’rhiod...Stopping beside the bed, he carefully unsheathed the two poisoned daggers and stepped out of the Unseen World into the waking. As he did, he became Luc. It seemed appropriate.
It also seems that Slayer is now on a mission to kill his nephew, Rand. Apparently, one of the Forsaken (identity unknown... now that’s new...) has him following Rand in the hopes of offing him, but it’s not really a priority. So, what is his ultimate mission? That’s still a mystery.