The Hero Twins were a celestial phenomenon made up of a binary black hole system. Located far from any known space lanes or hyperspace jump points, it was created after the collapse of two stars which formed accretion disks as the black holes orbited one another. The resultant gravitational field disrupted realspace causing the illusion that surrounding starfields were rotating around them.
In 17 BBY, it was the location of the first test of a weaponized version of Galen Erso's research into kyber crystal energy enhancement research as part of Project Celestial Power. Lieutenant Commander Orson Krennic headed the test aboard a requisitioned Imperial Star Destroyer accompanied by several researchers, including Reeva Demesne and Professor Sahali. This test confirmed the ability to harness kyber crystals for use in the Death Star's superlaser, leading to continued research to increase the weapon's energy output.
- Star Wars: Timelines