Aeterna is by far the oldest and most temporally anomalous object in the universe. Surrounded by a bubble of severely sped up time, it is approximately 101,500 years old, far older than the universe. Because of the time differential between Aeterna's sphere of influence and the rest of the universe, it is almost completely impossible for a spacecraft to enter it, because the first atom could orbit the object billions of times before the next even entered, resulting in any probes sent towards it to be shredded into fundamental particles.
Aeterna originally formed as a perfectly normal G-class star in the reaches of the Flower Galaxy. What planets it might have had are unknown, but it probably had a civilization. It carried on its merry way until the Lareas Alliance decided to test its time warp technology on this star system.
The formation of the time-warp bubble permanently sealed off the system from the rest of the universe, and from the outside the star appeared to expand into a red giant and promptly collapse into a white dwarf after just three seconds. No one was watching however, as the Lareas Alliance and all other life in the universe ceased to exist the exact moment it was turned on. Only a minute later, the white dwarf had cooled into a black dwarf.
Over the intervening period, quantum mechanics shenanigans caused every atom on the object to fuse or decay to iron, over periods so unimaginably long that the number of years required for this to occur wouldn't fit on a page. None know what happened to the civilization which existed in the system, but long-range scans have detected something very large around the Iron Star. Hypotheses for what this is include a matrioshka brain, defunct dyson swarm, or something even more bizarre. As of today, no one can figure out a way to penetrate the time bubble, so no one knows for sure what it is.