The Dark Lords are an unspeakably ancient evil force. There are believed to be four of them, to correspond to the four elements (earth, fire, wind, water) and in opposition to the four Monster Gods. However, just as the exact number of Monster Gods is not known with certainty, neither is the number of Dark Lords. They can be killed (as happened at numerous points during Antiquity, the Mage Wars, and even very occasionally during the Ages of the Alliance); but because of their incredible power and great destructive capacity, most of the Dark Lords were merely imprisoned, sealed, or bound in various ways.
Many stories of the dark lords come from an era called the "mythical age" in which the Monster Gods were said to have fought alongside the mortal races of the verse, helping to defeat or bind all of the Dark Lords. The Dark Lords, meanwhile, fought beside the cacodaemons of the Underworld, the Armies of Darkness, and the fabled Darkest Tower. While it is widely acknowledged that tales of the Darkest Tower pre-date the Mage Wars, most historians place little substance in the stories.
Regardless, the Dark Lords are widely known to have existed during Antiquity and to have caused great devastation. Up until the Sixth Age, most historians placed the events of the Mythical Age during Antiquity, and it was not until the late Sixth Age and the Age of the Dragon that archivists were able to properly separate the different accounts.
Throughout history, various cults have developed in worship of the Dark Lords. Informed by Daemons from the Underworlds, these cults hold that the Dark Lords have existed since the dawn of time. However, the Dark Lords being mortal, would require that their creation have taken place after the dawn of time.
It is generally agreed (by those not actively worshipping evil) that the Dark Lords were created at the beginning of the age of Myth, by the Iname.
The Dark Lords are described alternatively as either unintelligent beasts, or massively intelligent immortals. While they did not display much in the way of conventional reasoning, human interaction with them was, by and large, short.
Jason Bur'I described the Dark Lords as in possession of what he called 'the infinite nature'. He said: "They are not 'evil' in the way a man who kicks a dog, or a person who takes another's life is; they are operating on a level outside human perception. Our minds cannot grasp the infinite nature of these... things. To us, we see only the death and destruction they bring, yet to them, taking the time to kill a single one of us would show more care than they are even capable of".
Jason's opinions are informed by his having faced a dark lord and lived.
Dark Lords are largely immune to magic, but still somewhat susceptible. When a dark lord is "killed" the Shadow Lord moves to the far end of the spectrum, away from what killed it. EG, if dark magic is used, the lord becomes susceptible to light magic.
In order to "kill" a dark lord, one must first split it into eight pieces. This takes tremendous power, often requiring the assistance of a Monster God to accomplish. Each piece then must be fought and defeated separately, at which point it transforms into a Shadow Lord. Shadow Lords are nigh impossible to defeat, and nearly immune to magic. Conventional, enchanted weapons can hurt them, but they are extremely strong. No shadow lord has ever been pitted against modern weaponry, but anecdotal evidence suggests they should be vulnerable to being shot a bunch of times.
Legend holds that there are four Shadow Lords, but like the Monster Gods these "four" may merely be the pantheon or leaders, with dozens of less powerful dark lords beneath them. Since each Lord can be split into eight shards, it is difficult to distinguish in the various legends of a tale tells of a full dark lord, a 'lesser' dark lord, or merely a fragment. Further complicating matters is the existence of the Iron Reavers, which, while dating from around the Age of Darkness were frequently confused with Dark Lords.
Four are mentioned by name in the Course Books: Shabrindago, Ra, Nimi, and Sartec. In The Path to Ascension(Story), Hunter Jusenkyou refers to himself as the slayer of all four such Lords, though Nimi is the only one mentioned as a Dark Lord. However, his name being listed beside the four other beings would seem to indicate their status.