Graphic Novel
Published as Tales of the Jedi:
The Golden Age of the Sith.

This story is collected in:

Tales of the Jedi: Volume 1

Comic Book series
published July 1996, October 1996 thru February 1997 as Tales of the Jedi: The Golden Age of the Sith #0, 1, 2, 3, 4 & 5 by Dark Horse Comics:

Issue #0Issue #1

Issue #2Issue #3

Issue #4Issue #5

Synopsis:
THE GREAT HYPERSPACE WAR
Five millennia before Luke Skywalker was born and 1,000 years before two young Jedi reawakened a long-dormant evil, the dark power of the Sith held unquestioning rule over the galaxy. For those black-souled, corrupt Jedi, it was a golden age. For the rest of the galaxy, it was a nightmare.
Navigators and explorers are a special breed: they blaze the paths others will follow. They must have strength, drive, and hope, and be more than a little fearless. But nowhere is it written that they must have luck. Gav and Jori Daragon make their living charting the routes of hyperspace and selling those routes to traders and haulers. When a star-swarm cluster batters their ship, they land on the planet Cinnagar, destitute and forlorn, and convince the relatively amiable Aarrba the Hutt to make the necessary repairs.
Marka Ragnos ruled the galaxy with an iron fist. He was the Dark Lord of the Sith, the most powerful of the most powerful. But now he is dead. And two innocent hyperspace explorers, Gav and Jori Daragon, may follow suit if they get caught between the warring factions hoping to fill the Dark Lord void.
When Gav and Jori Daragon set off to map the uncharted regions of hyperspace, they knew they were risking their lives. But they thought it would be an unsuspected cluster of debris that would take them out of the game, not their successful discovery of a series of hyperspace "short cuts." The Sith Empire wants to know where these routes are, wants to hold the only map to these routes, so that it can maintain an iron grip on the galaxy. And the lives of a couple of explorers mean very little to these masters of the dark side of the Force.
When Gav and Jori Daragon were first captured by the evil Sith, they feared for their lives. Now, Jori fears for her brother's spirit, as would-be Dark Lord Naga Sadow begins to initiate him into the ways of the dark side of the Force. Naga Sadow is playing a deadly game of chess, and the Daragon siblings are his pawns.
Gav and Jori Daragon knew they could be killed in their chosen line of work: mapping out uncharted hyperspace flight paths could easily result in a deadly meeting with an unexpected meteorite shower or an unknown world. But it's neither comets nor planets that threaten them now. Rather, it's their success that may cost them their lives. They've successfully mapped a hyperspace shortcut, a shortcut which could prove strategically imperative in the event of war. And war is just what Gav and Jori have found themselves in the middle of. Trapped between two factions of the Sith, each vying for control of the galaxy, this sibling duo of hyperspace pioneers has become a pawn to the dark side of Sith magic.

Synopsis taken from Dark Horse Comics, www.darkhorse.com.