The First Stratos Contention was a conflict in the Stratos Distribution in the Unknown Regions. While it began as a power struggle among various Lugubraa mercenary factions and their backers, it became a war when one faction attacked Toriafas and Cheff and brought the wrath of the Golden Empire down on all the warring parties.
Historians in the Golden Empire believed the infighting began in late 155 or early 156 ABY, and was sparked by feuds between mercenary factions seeking to acquire both more territory and a reliable source of Lugubraa warriors. Most of those involved hired additional mercenary and pirate ships, but this fueled rather than deciding the conflict, because at least three mercenary companies and a gang of Ebruchi pirates sought to control territory themselves and joined battle against the other factions. Planets were taken and lost on a weekly basis, with most conquerors usually only trying to defend major settlements or simply feeding native populaces to their Lugubraa to keep numbers up.
In late 156 ABY, one of the factions attacked Toriafas. The Toriafas Defense Grid and the planet's defensive fleet forced the invaders into a hasty retreat, but Queen Rin Sakaros foresaw a followup attack on more lightly-guarded Cheff and sent Breek Zagrev there to deal with the situation. Breek won the Battle of Cheff, but at Sorrik's command, she and the captain of her flagship, Augu Pentag, allowed some of the Lugubraa to flee from the system so the Empire could plot their escape vectors.
The Empire strikes back
Rin raised the Chiss Centurion Vos'elk'eetash to the rank of Legate and gave her a battle group to deal with the situation. Pursuing the Lugubraa into the Stratos Distribution, Selkee and her forces hunted them for two months, winning what few engagements they could force but often failing to join battle. The Empire's force was larger than any single enemy fleet, though not all of them combined, and few mercenaries were foolish enough to stand their ground. The few land-based forces which tried were obliterated by Selkee's armies, led by Selkee herself, Aearbo Manitani, Rajj-Yo, and Hataphri Rahn Kazot, and spearheaded by Selkee's Garjo battle guard and the 4th and 17th Massassi Cohorts.
Eventually, the surviving mercenaries called a truce to combine their forces against the greatest enemy. They lured Selkee's fleet into a trap in an uninhabited system, but Selkee turned the tables on them, fleeing in-system as close to the system's primary as she dared and using the Force to trigger a solar flare. With all power to shields, the majority of her ships and crew survived. The Lugubraa and their mercenary allies were not so lucky; most ships were destroyed instantly, and the crews of those that weren't died off quickly from severe radiation poisoning.
A weather eye on the horizon
The Royal fleet limped back to the Empire; though she had wiped out most of the Empire's enemies in a single moment, Selkee's commanders pointed out that she lacked the forces to carve out a toehold in the Stratos Distribution itself. The Chiss agreed, but once her ships were repaired, she received permission from Sorrik to establish a forward base between the Empire's borders and the Stratos Distribution, which would serve as both a watchtower and a rapid response base. Selkee led her fleet to seize and garrison what became known as Ord Vos.
With their numbers so suddenly and drastically reduced, the surviving Lugubraa no longer had such acute competition for resources, and infighting among the various mercenary factions died off for a time.