Karlsu was a Human of the male variety. He served the Republic Military during the time of the Cold War against the Sith Empire. Stationed at Waypoint Station Aurek on Taris as a Lieutenant, Karlsu was a part of a commando squad tasked with escorting researchers into the destroyed remains of the Republic warship, the Endar Spire. As the sole survivor of his team, Karlsu provided assistance to a Republic-aligned person sent by Captain Childress in overcoming the pirate forces within the wrecked vessel.
Karlsu, a male Human, enlisted in the Republic Military sometime prior to the Cold War that occurred between the Galactic Republic and the Sith Empire. By 3643 BBY, Karlsu had achieved the rank of Lieutenant and was stationed on the planet of Taris. Serving under Captain Childress at Waypoint Station Aurek, he was a member of the security forces for the Taris Resettlement Initiative.
When Republic forces located the remnants of the Endar Spire, the Republic warship that Darth Malak had attacked over 300 years prior in an attempt to assassinate the Jedi Knight Bastila Shan, Captain Childress identified an opportunity to aid the Republic. Childress believed that the logs from the Spire, which had witnessed Malak's bombardment of the planet, would be invaluable in defending against future attacks similar to that on Taris, or the Sith's more recent Sacking of Coruscant. Consequently, he dispatched a team of researchers, accompanied by a commando unit, to the wreckage to recover the ship's logs.
However, a group of pirates and scavengers had already discovered the wreckage, and they attacked and killed the commandos. The researchers survived, so Childress dispatched another team to the Spire to expel the pirates. By the time a Republic-aligned individual arrived at Waypoint Station Aurek, the captain had dispatched a total of five teams into the ship, with Karlsu being a member of the fifth and final group.
The individual, who had resolved a land claim dispute in the Resettlement Project's main city of Olaris, was requested by Private Sakal to contact Childress. Childress requested that the individual locate the researchers and assist them in recovering the logs, so they journeyed to the wreckage and entered. The individual encountered Karlsu near the entrance, and the lieutenant, realizing that they were an ally, signaled the remaining researchers to emerge from hiding.
With the individual leading the way, Karlsu and the team progressed through the ruined ship toward the main computers. Karlsu and the individual fought off the pirates while the researchers retrieved the logs. After they defeated the pirates, Karlsu expressed his gratitude to the individual and assured them that he would safely transport the researchers and the data back to Aurek.
Lieutenant Karlsu's creation was for Star Wars: The Old Republic, a massively multiplayer online role-playing game that BioWare released on December 20, 2011. He makes an appearance in the Taris mission titled "Wake of the Spire," where Republic players escort him and a group of researchers through the pirate-infested ruins of the Endar Spire.