The Dominion of Darkness was a Dark Jedi organisation that eventually made itself into a Sith Order. They were responsible for several events within the galaxy, culminating in a New Sith Civil War and a Force Cold War, which ultimately destroyed the Order.
The Dominion of Darkness was founded from the dark days following the death of both Darth Sidious and Darth Vader at the First Battle of Endor. While one of Darth Vader's candidates for apprentice, Lumiya, secured the title of Dark Lord by defeating another candidate, Flint, the rest of the Dark Jedi Order attached to the Emperor's Empire found themselves rudderless. Made up of Hands that were personally loyal to the Emperor, Inquisitors whom represented the replacement for the Jedi, and psuedo-Sith named the Prophets of the Dark Side, the Dark Jedi suffered.
The death of the Emperor scattered the Hands, and, just before the death of the Emperor, the majority of the Prophets defected, abandoning the Empire. Several Prophets and Prophetesses remained, but many of the Inquisitors left the Empire for the warlord fiefdom the Pentastar Alignment, becoming InQuestors of Judgment. In short, the Dark Jedi Order was hulled.
However, the remaining Inquisitors and Prophets continued to serve the Empire, renewing the strength of the Order. A group of fake Prophets of the Dark Side were created as religious figureheads within the Dark Force religion, but they joined rogue Grand Moffs and Grand Admirals in opposing the Empire a year after Endor. In the subsequent civil war, the fake Prophets and Grand Moffs were executed, and the Empire consolidated strength from those entities. The Rebel Alliance, over, had secured much of the Outer and Mid Rims, and key worlds throughout the Inner Rim, Colonies and Core, and had Luke Skywalker - the most powerful Force user remaining.
Lumiya fled into hiding, but the tide turned when Lord Shadowspawn, a Prophet of the Dark Side whom had remained loyal to the Empire even in exile, returned with an army of Stormtroopers and fleet of warships. Conquering the Inner Rim, he rallied Inquisitors and Prophets to regain control of key worlds within the Core and Colonies - a Sith Order was coming about.
However, Lord Shadowspawn was defeated, and the Empire moved to policies which drove the remaining Prophets and Inquisitors away, into the Deep Core and Outer Rim. Forging alliances with the warlords, the Sith Order, nearly halted by Skywalker and the Empire, was born on Korriban, securing worlds throughout the Outer Rim, ready to crush both the Empire and the Alliance - the latter severely weakened by Shadowspawn's return.
Destruction and ShadowsEdit
A Senex Lord and Inquisitor named Garonnin declared himself 'Darth Sanguinis' with relics found on Korriban, triggering a power struggle within the Sith, inspired by Lumiya's secret actions. The leading Prophet, Garen Kya, declared himself 'Darth Rem' and pulled the Sith into civil war, even as they trounced the Alliance and Empire with their dark tactics. Lord Garonnin withdrew, taking with him Holocrons that Kya, in a fit of insanity, had actually given him. The Holocrons of Darth Millennial and Gorog considered Garonnin a pretender, and so would not speak to him of their legends and teachings - nor any of his spawn.
The Sith, their only legitimacy gained by holding a few relics which they could hardly use, withdrew to the Senex Sector, and prepared their revenge. Enticing Scarev Quest into the Dominion, even as he paraded around beside Lumiya and Carnox Jax, Lord Garonnin engaged in a plot to place the 'Emperor's son' on the Imperial Throne in 12 ABY, but was killed by the Dark Jedi, Irek at the direction of his mother. That death crippled the remaining Dark Jedi furthermore - especially with the loss of Quest and any position of strength within the Empire - but the remnants continued to engage in plots to disrupt the galaxy, placing the Scepter of Ragnos in the hands of the Reborn, inspiring a Sith uprising which cost the Jedi badly, albeit unsuccessfully restoring the Empire.
The Dark Jedi continued to hide in the shadows of the Senex Lords, deteriorating. They used the sectors economic strength to keep it independent, and to finance searches of Sith worlds which were all fruitless, consistently tied up in internal struggles under Darth Vassago and striving to find a system which would keep the Sith in contact; the Rule of the Strong was too divisive, the Rule of Two was too dangerous, the variations of the former were inaccessible to them, and they thinned their own ranks into the death of the new Sith Order. Then, in 60 ABY, the remaining Dark Jedi came across a little known world named Rakata Prime.
The Dominion is BornEdit
In 60 ABY, the Dark Jedi, having stretched their resources to the limit and still in possession of Sith Holocrons which would not cooperate, were at breaking point. However, it was on Rakata Prime, the dead and abandoned world of the Empire of Darth Revan, that they made a remarkable discovery. A Temple, adorned with only the beginnings of Sith glyphs, which revealed itself to the order, drawing them there.
They discovered this Temple had been constructed during the Hundred Year Darkness by Ajunta Pall as his resting place, before the Dark Jedi were routed from the Star Forge by internal fighting. The Temple had been abandoned, until it was discovered by Darth Malak, whom, intending to convert Rakata Prime into a new Korriban, made it his tomb and made efforts to convert it into a dark side nexus. In there the Dark Jedi discovered the Holocrons of Ajunta Pall and Darth Voren, a Sith apprentice of Darth Revan's whom was killed by Bastila before he could usurp the mantle.
These Holocrons were more willing to teach the Dark Jedi, and, when they reached true Sith status, the Holocrons of Darth Millennial and Gorog yielded their knowledge, at long last. The Sith Council resolved the last wave of internal issues and reformed into the House of Sith Lords, a trio of Sith dedicated to serving the Dark Lord of Chaos, and the Dominion of Darkness finally came into being.
Darth Insipid was a Sith destined to shake up the galaxy. Recruited into the One Sith, Insipid managed to garner enough support within the order to go on an extended mission within the Dominion of Darkness, taking with him Darth Idoneus and Darth Ardeur, the foundations of the Vapid, his own Sith faction. Insipid carefully placed the three of them in positions of power circa 55 ABY, himself laying the groundwork for his arrival by enacting a New Sith Civil War with the Senex sector and deposing the Dark Lord - Darth Vassago. Vassago and his followers fled, eventually setting up the Acolytes of Darkness splinter group on Ziost.
With the Sith on Lehon, his Sith began accruing more power, reporting to Darth Krayt that the Dominion were harmless, but suggesting they had links to a much larger group. Using the Dominion's Sith Holocrons, the three Sith grew powerful, supporting Darth Mystique as the Dark Lord of the Sith, taking places on the Sith Council beside Darth Harestisch and Darth Verrick.
Eventually Insipid rose to become equal to the Dark Lord, disposing of the Council entirely, before Darth Harestisch took the throne, reorganising the Sith into a House of Lords. Dubbed the Dark Lord of Betrayal, Insipid began setting up schemes involving his apprentice, Darth Avarice and preparing to launch a coup against Krayt. In 65 ABY he and the other One Sith agents were recalled before sufficient numbers had been gathered to destroy the One Sith, and so he and his other Vapid launched a sneak strike, using Darth Ardeur's conflicted loyalty to distract the Dark Lord while they stole three Sith Holocrons - those of Darth Andeddu, Darth Nihilus and Darth Bane.
With this victory likely to cause the Dominion to be targeted, Insipid sent his group into hiding on Bosthirda, placing them in stasis - Ardeur forcibly. The One Sith approached the Dominion secretly, noticing that the Vapid were nowhere nearby, but keeping tabs on this group, knowing it would be useful later.
Insipid hid on Coruscant, and returned in 95 ABY to resume his position within it - Lord Harestisch still the Dark Lord, uncontested. Quickly taking advantage of the Jedi imbalance - and all but daring the One Sith to emerge from hiding to stop him - Insipid, as the public official of the Dominion, convinced the Dark Lord to move the base of the Dominion to Nyssa, within the Tapani Sector, triggering a Force Cold War.
The Dominion, from the Senex sectors, Tapani Sector and with a secret reserve base in the Unknown Regions at Lehon, prepared for galactic dominance at last. Expanding into the Bothan Sector, the Dominion grew stronger, imbalancing the Empire and GA until the Templars of Twilight devastated Nyssa, and the Dominion remnants were forced back into hiding.