Moridin is Ishamael. Cyndane is Lanfear. Osan'gar is Aginor, and is Corlan Dashiva. The Daughter of the Nine Moons is one of the Seanchean Empress's children.
Raserei says: Wow, thank you Captain Obvious. But, only 1 out of four has been proved. So, better luck next time.
Comments
Too right! Four out of four, mate! To specify something, the DoTNM is Tuon, the Empress' daughter. Obvious, true, but it's good to see them posted instead of just assuming "everyone knows".
Ruriha 
1. Cyndane is Lanfear. Taking into account several other theories also mentioned on this page as well as the following "kicker" from WH. I feel it is safe to say Cyndane is Lanfear.
a. (p641) So he had found a woman to use the other access key. She would have faced the Great Lord - faced the Creator!-with him. She would have shard the power with him, let him rule the world at her side. And he spurned her love, spurned her!
This is obvilously Lanfear since she made the above offer to Rand and he spurned her.
b. (p649) She was stronder than Cyndane had been before the Aelfinn and Eelfinn held her!
I believe this is to be a reference to Lanfear's time in the Finn world after being pushed through by Moiraine. The question is where is Moiraine?
2. Osan'gar is Aginor and Corlan Dashiva. This one is also from WH and is pretty much stated point blank.
a. (p645) Crouching behind a fallen log, Osan'gar panted for the exertion of running. Those months masquerading as Corlan Dashiva had not made him any fonder of exercise.
3. Daughter of Nine Moons is Tuon.
So good jome Patrick. 
People usually notice the sentence where it says that Moridin "had often seemed to believe he was [the Dark One]" just like Ishamael. But there is a better proof next line: "and the boy's face he wore now gad not changed that"; which means that Demandred knew him before as one of the Chosen.
Well, but it is obious.
Whitefire.
Ishamael had been high on Dark One's list, with power only equalled/better by Dragon, so if Dark one could bring back people from dead, he would be of prime importance, and alot more likely than getting some new guy completely unknown to everyone to leap into Nae'Blis position.
Moridin/Ishamael's spiritual advisor.
Jedi Knight
Proud Warder to Tatayana and Lanfear81.
In love with a beautiful English lady.
I don't know why everyone things Lanfear died! The thing I find funny about it is everyone says *and I agree* that Moiraine is living, but if one could live through the Finn's hospitality, why couldn't two? Both are strong enough, and isn't Lanfear stronger than Moiraine? So if one person had to have died, I would think it would be Moiraine, and since she can't have died, lets face it, she's too cool and Rand needs her, both have to be alive!
*If anyone has proof stating that Lanfear is dead, sorry I missed it, I really need to reread the books*
To answer arangin's post, there's no PROOF that Lanfear died. There is evidence. Why put her in Cyndane's body if she didn't die? Why weaken her strength in the Power if she didn't die? Why mindtrap her if she hadn't failed in something important?
As for who had the better chance of living through the trip to the Eelfinn, as the two women fell through the doorway Moiraine snatched the bracelet angreal from Lanfear's wrist. Moiraine has an angreal of her own already at work, so there's a significant chance that at that point she's stronger than Lanfear. Also, isn't it implied somewhere that the *Finns aren't very hospitable to the Shadow? Egwene warns Mat about what manner of questions he can safely ask, and although my memory is poor on the details it seemed that questions about the Forsaken or Shadowspawn would not be well received. Well, how much more one of them in the flesh? Anyway, that's all conjecture, but I lean strongly to Lanfear dying among the *Finns, the Lord of the Grave bringing her back as Cyndane, and Moiraine still alive in *Finnland.
Call me Tim
If anyone doesn't think that Aginor is Osan'gar(Which I doubt anyone does, but who cares)I have more on the topic. In WH, Chapter 35 With the Choedan Kal, page 645, Osan'gar thinks "He had never been a soldier, not really. His talants, his genius, lay elsewhere. The Trollocs were his making, and thus the Myrddraal that had sprung from them, and other creatures that had rocked the world and made his name famous." This states that Osan'gar made the Shadowspawn, the achievement that made Aginor famous.
Eben Hopwil
And Demandred is _not_ Taim! At the end of WH he goes towards Rand/Ny when they are using the Choden Kal keys, and he sees Damer Flinn (one of the first Asha'man Taim recruited) and doesn't recognise him (it takes him the best part of a page to work out that Flinn is an Asha'man!)
And so dies the most annoying thoery ever created
The Daughter of the Nine Moons issue should of been clear to anyone re-reading The Great Hunt, as they make reference to the Court of the Nine Moons. I hope you are wrong about the fourth prediction, as I don't like the idea of Moridan being Ishamael.
*waves a little flag on a stick* hooray!
I will try. Before surrendering to dreams or death, I will try.
..yes, he's a male forsaken. No, he's not Demandred or Osan'gar. That doesn't leave too many to choose from. So, Taim = Moridin = Ishamael. I think that if the gars are brought into being end Bk5, why would the DO not bring Ishy back at the same time? Obviously, there must have been a real Mazrim Taim, but i think he's been left for dead somewhere and it's now the Nae'blis himself who's the M'Hael. I've written a breif theory to this effect, but w/out much substantiating evidence. it just seems obvious that Taim is one of the Chosen, he is male, and there's not too many to choose from. Just because Moridin doesn't appear in the bks til after LOC doesn't mean he wasn't already active. Unless Taim is Asmodean, which i think would be very lame, and anyway, the personalities are wrong.
Baphomet 23
Give me the strength to change the things I can, the grace to accept the things I cannot, and a great big bag of money.
My online gallery:
http://daveb23.deviantart.com/gallery/
MUCH BETTER PROOFIN WINTER'S HEART BUT SOME OF IT IS "CIRCUMSTANTIAL"
I'd be giving him 4 out of 4. The only valid debate seems to be whether Ishamael is Moridin or not, but the fact of his 'preferred' treatment as compared to the other of the chosen and the fact that he is a regular user of the TP shows that he is most likely Ishamael then not.
Jahar Narishma 
Shara is actually inhabited by bannanas 
The Band of the Red Hand is made of Ninjas like Mat
;
YES!!!