One of the many unfortunate cases of extraterrestrial civilizations essentially dooming themselves came in the form of this planet, named Kar'tise by scientists aboard the WDS Isvoy, discovered in 9450CE during their mission to chart new life forms in that galaxy. At first, it wasn't known just what happened to this world, which seemed to have all kinds of wreckage in orbit. The Isvoy decided to stay here to figure out what exactly happenned to this planet, as obviously before...something destroyed it, there was a thriving civilization here. 2 weeks of study provided much needed answers.
It is estimated this event took place at least 1.2 million Earth years ago. There is evidence that this planet was the home of a Late Type-2 civilization, from scanning the surface of the planet. Nothing of them remained planetside, however. Fragments of some kind of machinery returned from the surface offered some clues. The piece of metal seemed like a recording device, and was sent for analysis. The information retrieved from this recording device was badly damaged, but enough was recoverable to paint a bleak picture of what happened.
Events Leading to the Destruction
It appears that the species living on this planet called themselves the Karuegi, and derived their power from a Dyson Swarm around their sun. Apparently, this also prevented solar flares from affecting the planet. The Dyson Swarm around the star was also finely tuned, so that the Karuegi could increase or decrease the power output of their star as needed. One day, one of the small spacecraft making up the dyson swarm malfunctioned, during a crucial test, which made every single craft in the swarm report a problem and offline themselves. The sudden power loss made the central star start throwing off solar flares violently, and caused a runaway chain reaction The flares increased in severity, turning into a plasma wave which ripped through the system, sterilizing every single planet it touched.
In the end, the central star was a DQ9.1-class white dwarf, and the entire system was irreversably ruined. Kar'tise itself suffered the worst of it, its single moon fragmenting into a wide ring and several asteroids, and the planet itself almost completely losing its atmosphere. The Karuegi tried to evacuate, as evidenced by the ship wreckage in orbit, but were too late. Even on the surface were wrecks of orbital ships that crashed attempting to make orbit when the plasma wave hit.
A bunker that was dug into one of the mountains planetside just in case this very scenario happened, was also doomed. It was estimated that around 1,200 Karuegi evacuated here, but the plasma wave that rocked the planet also caused a small breach in the atmospheric pressure regulator. It was only a tiny breach, but it was enough to ensure the demise of every single Karuegi that evacuated to the bunker, within 10 local years.
The only thing that survived the destruction was an automated radiation-resistant S.O.S. beacon in orbit around the last planet in the system, warning would-be explorers to stay away, as some asteroids in the system were still radioactive. The crew of the Isvoy then held a small memorial, for the Karuegi they never met aside from some damaged recordings. A tiny automated station was also released, to monitor this planet for any signs of recovery, no matter how unlikely.
The Isvoy left after their study was completed.