Strengths and Talents
Demandred, one of the thirteen original Forsaken, was born some 400 years before the War of Shadow with the name Barid Bel Medar.
Barid Bel Medar was tall, with dark hair and a hawk-nose. He was considered to be handsome, though not as much so as was Lews Therin Telamon, the man that Barid Bel hated most. (Guide). (Bashere? maybe)
In order to fully understand the man who would one day become Demandred, it is necessary to first understand his overwhelming hatred of Lews Therin Telamon. Barid Bel's life seemed to made up of 'almost' and 'not quite'. He wasn't as tall, nor as handsome as Lews Therin. He wasn't as talented or skilled as Lews Therin. Everything that Barid Bel could do, Lews Therin could do better.
Demandred was an acclaimed man, one of the most acclaimed of his age. He held several public offices, and is known to have written books on a wide variety of subjects during the Age of Legends, for which he received both critical and popular acclaim.
When the War of Power began, Barid Bel started out opposing the Shadow. For the first three years of the war, he was a high-ranking general within the army, due to his strategic vision and tactical flair. The only thing that kept him from surpassing Lews Therin in this area was that he was a gambler, and put too much stock in taking risks.
When Lews Therin was promoted above him, Barid Bel was, of course, disgusted. Angry, he once went so far as to say that, with Lews Therin in charge, the Shadow had a better chance of winning. It was Lews Therin's promotion that finally pushed him over the edge. He traveled to Shayol Ghul to pledge his soul to the Dark One, and took the name Demandred. (The Fires of Heaven, Chapter 3.)
After turning, Demandred turned his skills as a military general against the forces that he had previously fought along-side with. He turned out to be as good a general for the Shadow as he had been against it. (Guide) He also acted as governor over conquered territory several times, but always he returned to the battlefield; he wanted to be the one to personally kill Lews Therin Telamon.
During the War of Power, Demandred committed many heinous crimes. One of the most notorious incidents was capturing two cities and feeding them to the Trollocs. His reason? He believed that they had slighted him before the war. (Lord of Chaos, Chapter 2.) To him, this was a completely suitable fate for these people. Demandred believed that anyone who slighted him should be punished.
Like all of the other Forsaken, Demandred holds high hopes of being named Nae'blis. Though that hope must have been dimmed somewhat upon Moridin's ascension, he no doubt still hopes that he may one day achieve this station.
-Barid Bel was born some 400 years before the War of Power. (Guide)
-Three years after the beginning of the War of Power, Barid Bel turns to the Shadow. (Lord of Chaos, Prologue.)
-Demandred and the other Forsaken are sealed into the Bore at Shayol Ghul. (???)
-Demandred escapes from the Bore. (Time Unknown.)
-Demandred meets Shaidar Haran at Shayol Ghul and speaks to the Dark One, who tempts him with the title of Nae'blis and gives him his orders. (Lord of Chaos, Prologue.)
-Demandred meets with Mesaana, Graendal and Semirhage and passes on his orders from the Dark Lord. (Lord of Chaos, Prologue.)
-Demandred meets again with Mesaana and Graendal. (Lord of Chaos, Chapter 6.)
-Demandred once again travels to Shayol Ghul. (Lord of Chaos, Epilogue.)
-Demandred meets with Graendal, Osan'gar and Aran'gar. Moridin and Cyndane also show up. (Winter's Heart, Chapter 13.)
-Demandred goes to Shadar Logoth in an attempt to stop Rand from cleansing saidin. (Winter's Heart, Chapter 35.)
Strengths and Talents
Like all of the other Forsaken, Demandred is very strong in the One Power, stronger than most of the men who can channel in today's world. We do not know his exact standing among the Forsaken, but it is safe to say that, no matter how powerful a channeler he is, he is less powerful than Ishamael and Moridin.
He is also known to have a talent that only three other's possess: Lews Therin (and therefore Rand) and Semirhage. This talent is to be able to block a gateway open, as Rand did when Aviendha ran away from him. (The Fires of Heaven, Chapter 32.)
Aside from the One Power, Demandred was a good military general. He had the skills and intellect, and put them to good use both for the Light, and against the Light.
Relationships with Other Characters
Demandred hated Lews Therin Telamon with a deep vengeance, his only reason being that Lews Therin achieved greater success than he did. Demandred is also known to have wanted Ilyena, Lews Therin's wife, to himself. All in all, Lews Therin was the reason that Demandred turned to the Shadow.
Demandred hates Rand as he hated Lews Therin. His hatred pretty much simply shifts from one to the other.
He is not known to have a particularly good relationship with the other Forsaken, especially Sammael. This most likely arises from the fact that, during the War of Power, both Demandred and Sammael were military generals, and both wanted the honor of killing Lews Therin.
Demandred, Mesaana and Semirhage have formed a loose alliance in which they have decided to eliminate all of the other Forsaken before turning on each other. (Winter's Heart, Chapter 13.)
Over time, many theories have been developed as to Demandred's identity and location.
One of the most popular theories is that Demandred has disguised himself as Mazrim Taim. There has been a lot of evidence as to this throughout the series. What better way to get revenge on Lews Therin Telamon/Rand al'Thor than to get close to him, and then back stab him? Also, Mazrim Taim ordered Rand's death in Winter's Heart. However, this theory came to an end when Robert Jordan came out and said that Demandred and Mazrim Taim are not the same person.
Another theory is that Demandred has placed himself with the Whitecloaks. As of now, we have had Forsaken scattered all over the world: Semirhage most likely in Seanchan, Mesaana in the White Tower, Graendal in Arad Domon, Sammael in Illian, Rhavin in Andor, and so on and so forth. But we have not yet seen any of them dealing with the Children of the Light. As for his exact identity, with this theory, it could be anyone.
Some people also believe that Demandred is working with Semirhage in Seanchan. To support this, there is the fact that Demandred, Mesaana and Semirhage are loosely allied.
Shara is also in the running, too, it seems. As with the argument for the Children of the Light, as of yet, only Graendal has shown the slightest interest in Shara. Once again, it would be a territory that no one has claimed, so to speak.
And of course, the Sea Folk. Once again, no other Forsaken are involved with them, that we know of. As the Sea Folk control a large number of women who can channel, it could prove a temptation to any of the Forsaken. There is no other proof for this theory.
With all of the theories as to Demandred's identity floating around, it is impossible to say who he is. Any of the above theories could be correct, or he could be disguised as someone else. There is also the possibility that he is simply not masquerading as anyone or anything. Ishamael has done it; Demandred could be doing the same.
In the words of Robert Jordan, I suppose we will just have to read and find out.
-Barid Bel Medar was born one day after Lews Therin Telamon. (Lord of Chaos, Prologue.)
-Barid Bel's hatred and jealousy grew with every honor that Lews Therin awarded him. (Guide.)
"Should I expect more, Lanfear? Have you convinced Demandred to stop thinking he is all but the Great Lord's heir?" (Rahvin to Lanfear.) (The Fires of Heaven, Prologue.)
"Great Lord, the Dragon can be destroyed. He is ignorant and weak, scattering his attentions in a dozen directions." (Demandred to the Dark One) (Lord of Chaos, Prologue.)
"How much has the Great Lord known, for how long? How much of what has happened has been at his design all along?" (Demandred to Mesaana, Semirhage, Graendal) (Lord of Chaos, Prologue.)
"Let the Lord of Chaos rule." (Demandred to himself.) (Lord of Chaos, Chapter 7.)
"Why have you called us here? I have much to do, and no time for idle talk." (Demandred to Moridin.) (Winter's Heart, Chapter 13.)