Mentioned in Star Wars books, this is the valley where tombs of the Sith Dark Lords might be found, and is where the Eternal Flame is located. (This Flame being of our own creation here at the Escapepod role play boards.)Originally on Korriban, the Valley of the Dark Lords was brought in its entirety into the Darker Realms by Dark Lord Roan, that his children by himself and Graysith, inherent in the All, could use the strength of the Eternal Flame to bring the Sith civilization back to life. It is a long valley, rocky and desolate, with winding side tributaries laden with bench and talus slopes. Not one lick of water or greenery enhances it; it is approximately one kilometer deep, 25 kilometers long, 6 kilometers across from lip to lip, but a mere 100 yards (at its widest) at the bottom.
The Valley of the Dark Lords, according to Lucas, was where the tombs of fallen Sith Lords were built. From this we extrapolate backwards, having it thus contain the tombs of the Dark Lords of the Sith (Warrior, Sorcerer, and Armorer) which pre-date those in Lucas' SW universe. At the head of the canyon, at the mouth which is strangely the deepest portion of it, lies the Eternal Flame (see descriptions). As one progresses away from this flame one walks below and past the tombs of the Dark Lords of the Sith, tombs complete with carven statuary representing them, following history as one goes along until at the other end one finds the newest tombs, that of Darths Vader, Andeddu, and XoXaan.
It should be noted that some of the original tombs have been ransacked by the dark jedi when they discovered this place. However, they appear in glorious completeness to those coming into the Valley to use the Flame for its intended purpose, a secret well guarded by the original race of the Sith (of our boards). Ignited by the intent of the incoming user, the carven statues appear whole, and their eyes glow in the original multi-colored hues of the Sith Lords.
To all others, unless the secret is known, the Valley is simply a place of tombs, with a flame at one end that appears merely to be a tribute to those dead Lords.