Alsakan was once an ecumenopolis in the Alsakan system in the Core Worlds, on the Perlemian Trade Route.
The planet was originally a Killik colony before 30,000 BBY when they were taken to the Unknown Regions, possibly by the Celestials in 30,000 BBY. At least one Killik from Alsakan became a user of the Dark Side and was able to escape the world and flee to Sarafur.
In 26,000 BBY Alsakan was colonized by Humans from Coruscant in the colony ship Kuat Explorer. The planet was divided into many kingdoms until the King of Archais united the planet after the Battle of the Ten Valleys. Alsakan became a Core Founder of the Galactic Republic in 25,053 BBY.
From 17,000 BBY until 3,017 BBY, Alsakan tried to usurp Coruscant's predominance seventeen times, causing the Alsakan Conflicts between the planets' holdings in the Expansion Region.
In 1,000 BBY, the Alsakan Tessent was carved to commemorate the Battle of the Ten Valleys. Native Dark Jedi Jilst Bindalin stole the Tessent and took it to the tomb of the Killik darksider on Sarafur, whom Bindalin believed to have been a Sith Lord.
While a member of the Galactic Empire, Alsakan was one of the first Imperial worlds to quickly surrender to Admiral Ackbar's New Republic fleet. As Coruscant changed sides over the intervening years, Alsakan was quick to follow its lead, professing loyalty to whomever controlled Coruscant.
In 18 ABY, Alsakan became one of the worst tragedies of the War of Darkness. The Dark Lord Sivter announced that the Cult of Shadow would wipe Alsakan clean of all life. Despite a combined effort by the Empire, New Republic, Jedi Order, and other smaller governments to stop him, Sivter was able to carry through with his promise by unexpectedly unleashing the Charon.
The Battle of Alsakan became a massacre of undreamt of proportions, making the cult’s earlier actions on Vorzyd V pale in comparison. All one trillion lives on the planet that hadn’t evacuated were killed by the Charon. By the time the battle was over, Alsakan had been reduced to a lifeless rock.