The Dread Empire, also called the Sith Empire, was a Medieval empire that spanned the Perseus Arm and came into direct conflict with The Old Republic. It was controlled by the Dread Emperor and his Dread Masters, who were all adept at soul-channelling dark impulses into various powers to inflict upon the physical world. The term sith became so iconic for this, that it would become a colloquialism for Aos Sí in later centuries.
See also: Orinoco Flow
The planet Orinoco Flow is blanketed almost entirely in one continuous ocean that flows across the planet's surface in a single direction. Only a narrow strip of land, at the tail end of the ocean's current, would be habitable for a month's length before being swallowed by the colossal wave at the head of the ocean's continual flow. This was why the Dread Empire staged its military from their base on this world, as it would be difficult to assault. Their primary base there was the Dread Fortress[Leg 1].
See also: Orinoco Flow#Dread Fortress
Usually concealed by the ocean, the Dread Fortress was the military stronghold for the Dread Empire. It was chosen to be on Orinoco Flow so that assault would be much harder by enemies of the empire. It looked like a blackened castle - charred by dark, evil flames. It had many twisted spires and seemed the epitome of every stereotypical evil aesthetic[Leg 1].
See also: Dread Emperor
See also: Dread Masters
The Dread Masters controlled a technologically advanced fighting force of well-armed soldiers. They commonly used plasma-based projectile weapons[Leg 2].
Legends of the NeSiverse
When King Arthur of Space Britain met with the people of The Old Republic on Coruscant he learnt of the Sith Empire. He ventured on a quest to defeat the empire and free the Perseus Arm from the tyranny of the Dread Emperor himself when they launched their assault upon the Dread Fortress of Orinoco Flow[Leg 1].
"As we already had the New Republic and the Galactic Empire for the modern era of NeS stories we wanted to use old era material from the Star Wars[Ext 1] franchise for the Medieval Era in which Space Camelot takes place. As well as The Old Republic, Al Ciao the Writer suggested the use of the Dread Masters[Ext 2], which formed the loose inspiration for our own Dread Masters of NeS lore." ~ Britt the Writer