Hearthpwn

Arfus?

if it's that you could have just hinted doge and all this pain would have been avoided

Something in common with The Lich King? Could it be... Ysera?

My last guess and then I concede...Kel'Thuzad ?

This is impossible

Thrall, Deathseer?

Dopplegangster

or

Echoing Ooze

I guess concede is not happening.. Lets see... I have a brand new theory!

Illidan Stormrage

-orb? Orb of Kil'jaeden? An orb he was given to by Kil'jaeden, presumably to defeat the Lich King

-number? That could mean almost anything, but everywhere can be seen that Illidan was imprisoned for 10k years - which is not for a charm indeed.

-others? (like him?) I mean, in WoW you have a whole class named Demon Hunter which is based on Illidan's "dog tag".

-you have met them before? (+LK hint) Above... And about LK hint, he fought and almost defeated Lich King/Arthas

-one of a kind? it takes two to carry? such ego .. He is one of a kind since hes the only one who has and can have Skull of Gul'dan. Dunno about that two to carry (maybe his nickname The Child of Light and Shadow) but his "You are not prepared" is kinda egoistic.

-maligned strength? big price? He is one of the most powerful entities in WoW when measured by the lore power and he had his eyes burned by Sargeras in exchange for immense power (big price)

-is XXX hiding in the shadows on purpose, or? finally (3rd verse)? That sentence that he will break from the shadow may refer to his imprisonment by Wardens led by Maiev Shadowsong (see the shadow there?) And his hiding on purpose - well he is "kinda" hiding in the Outland in his Black Temple. He said exactly "Perhaps hiding here was not the most prudent decision." Here meaning the Outland.

Just a theory tho...

Quote from Ashmogh >>

I guess concede is not happening.. Lets see... I have a brand new theory!

Illidan Stormrage

-orb? Orb of Kil'jaeden? An orb he was given to by Kil'jaeden, presumably to defeat the Lich King

-number? That could mean almost anything, but everywhere can be seen that Illidan was imprisoned for 10k years - which is not for a charm indeed.

-others? (like him?) I mean, in WoW you have a whole class named Demon Hunter which is based on Illidan's "dog tag".

-you have met them before? (+LK hint) Above... And about LK hint, he fought and almost defeated Lich King/Arthas

-one of a kind? it takes two to carry? such ego .. He is one of a kind since hes the only one who has and can have Skull of Gul'dan. Dunno about that two to carry (maybe his nickname The Child of Light and Shadow) but his "You are not prepared" is kinda egoistic.

-maligned strength? big price? He is one of the most powerful entities in WoW when measured by the lore power and he had his eyes burned by Sargeras in exchange for immense power (big price)

-is XXX hiding in the shadows on purpose, or? finally (3rd verse)? That sentence that he will break from the shadow may refer to his imprisonment by Wardens led by Maiev Shadowsong (see the shadow there?) And his hiding on purpose - well he is "kinda" hiding in the Outland in his Black Temple. He said exactly "Perhaps hiding here was not the most prudent decision." Here meaning the Outland.

Just a theory tho...

 A GAME THEORY!

(Sorry, i had to do it)

 

Dang it! Hunt is still on I guess...

Could it be Val'Kyr twins? Fjola Lightbane and Eydis Darkbane. 

1st verse could reffer to the dark and light orbs that will harm players during the encounter. 

"I may resemble the others,
"I may be invincible only when we are one,
but I'm one of a kind!

There are other Val'kyrs in World of Warcraft but Fjola and Eydis are unique. Also they might be invincible when they are together because of the debuffs. 

They have strong connection to Lich King as they are his servents. 

I just realised that you wrote "Others? Like him?" Is that a hint that we are looking for a male character or did you just accidentaly wrote "Him"? 

Blood of The Ancient One?

Mal'Ganis is my guess, if  not him, Illidan Stormrage