In the year 3258 B.E. an exploration ship crewed by Nath-el and W'hoorn was exploring the vast, starless reaches of the Permian Abyss. They were seeking to explain the irrational feelings of repulsion both the Nath-el and the Oteel had repeatedly and persistently reported feeling when passing near the Abyss.
Although the black expanses of the Permian Abyss appeared empty aside from space dust, logic dictated that something must be causing this feeling. Bringing along W'hoorn allies in case the Nath-el were overwhelmed by their revulsion, the Nath-el ship, commanded by Commander Atse Bent, entered the Abyss, aiming itself in the direction of the feeling.
As the weeks passed, the Nath-el grew increasingly uncomfortable until, as they approached their ultimate destination, most of the Nath-el fell into a coma-like state, while those that resisted were nigh-useless.
Finally, they arrived at their destination - an airless moon, but without a planet or star for it to orbit. It was covered in huge energy-laden technology recognizable as having been built by the Vyar, but with a purpose shrouded in mystery. It was what we now know as the Sheol Locus.
Having discovered what they came for, recognizing that they lacked the resources to unlock the secrets of this moon-spanning technology, and not wishing their Nath-el comrades further harm, the W'hoorn piloted the ship out of the Permian Abyss and back to civilization. As they sped away from the Sheol Locus, most of the Nath-el came out of their comas, though a few remained in them for the rest of their lives.
Over the course of the next 17 years, multiple expeditions, from a variety of races, arrived at the Sheol Locus to investigate what this ancient, unfathomable technology may be.
One of these expeditions was led by the Krona - a famously impatient race fond of blunt solutions. The Krona have saying - "Why go around something when you can just go through it?" Arriving at the Locus, they quickly had enough of the endless probing, experimenting, and discussion, and determined they would take unilateral action.
They attempted to cut into a part of it, trying and failing with both neutron welders and kithblades. Their very limited patience exhausted by these restrained half-measures, they decided to simply blow up part of it to see what's inside. While fusion bombs had no effect, gravity munitions did the trick, destroying a small portion of it.
To the Krona's dismay, however, what they discovered in the wreckage did not help them at all. Indeed, none of the Younger Races have ever been able to discern how the Locus worked or even what it's built of, much like the Void Gates, which were also constructed by the Vyar.
To all appearances, the damage the Sheol Locus sustained didn't shut it down, but in the coming years Nath-el and Oteel both reported that the feelings of repulsion they had long felt near the Permian Abyss had entirely disappeared. Something had changed.
What the Younger Races didn't know was that the Vyar and built the Sheol Locus specifically to repel the Cleax. It effectively put out an incredibly strong signal that the Cleax's biology found utterly repellent, keeping them out of Starmourn sector for the nearly 900,000 years since it had been constructed. As the Y'saari would later explain after having discovered what the impetuous Younger Races had done, the Locus had been built in the Permian Abyss because its technology required an area as free from gravitational fields as possible - thus why the gravity munitions were able to damage it.
39 years later, in 3202 B.E. the Cleax invaded Starmourn for the second time in the Second Cleax Invasion.