Great Dark
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(From WoWWiki)
The empty void between worlds. The first of everything when there was nothing.
Source of the energies of the Well of Eternity.
Part of the primary material dimension, as opposed to the Twisting Nether.
The Titans probably travel through the Great Dark, as opposed to the Twisting Nether (hence, their shock at the emergence of the Eredar).
It's basically the Warcraft universe version of outer space. Also refered to as the Great Dark Beyond.
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Great Dark vs. Twisting Nether
Aegwynn, in her narrative at the start of the Second War, referred to the Great Dark in much the way later sources established the Twisting Nether, so we can assume it was an error. The alternative, that there are forces in the Great Dark to rival the Burning Legion and oppose the Titans, is quite chilling. Sadly, this analysis may be true; the Titans sent only Sargeras to deal with the Eredar and Nathrezim, and it may be they were dealing with an even more pressing threat.
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Twisting Nether
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(From WoWWiki)
A dimension separate, but intertwined with the primary material dimension (where your Player character lives most of the time). Not to be confused with the Great Dark.
Shamans can warp to their hearth location using the Twisting Nether by casting the spell Astral Recall.
From chapter 1
(
http://www.worldofwarcraft.com/info/story/chapter1.html) of the World of Warcraft story from the official site, the Twisting Nether is described as:
[An ethereal dimension of chaotic magics that connected the myriad worlds of the universe, and
Home to an infinite number of malefic, demonic beings who sought only to destroy life and devour the energies of the living universe.]
The Twisting Nether surrounds all, though it remains invisible and unknowable. It is a realm of chaos, where colored, misty clouds and bright streamers mingle into a muted form that teases mortal minds. Innumerable worlds, including Azeroth, exist within the Twisting Nether, and many speculate that its protean energies are the stuff that creates existence. Magic currents are strong in the Nether, for it is demonic magic’s birthplace. Demons have their genesis in the Twisting Nether. They alone control its secrets and master its energies, using it as weapon, armor and cloak. They feel it through its madness, invading planes and whispering dark things to mortals on countless worlds.
Some say that the Titans also live in the Twisting Nether, but if this is true they seem content to let the Legion run wild. Other creatures, made of energy and lunacy, also stem from the Nether's winds. To travelers, the Twisting Nether can be a doorway to other worlds. It is a dangerous path, however; demons and other creatures threaten wanderers, and the plane itself causes the mind to recoil when asked to navigate its wonders. Chaos seethes in the Nether, and only the powerful can exert control.
Retrieved from "
http://www.wowwiki.com/Twisting_Nether"
