There aren’t any official resources about them that you’ll find anywhere online at this time, but I personally put together a large compilation a while back that might be of use - though it’s a bit outdated, only containing info up to Chapter 1 of invasion:
To summarize though:
The people who became the Triglav inhabited New Eden until some time near the end of the Second Jove Empire (a couple of thousand years ago), and were seemingly forced to take refuge in the Abyss aboard their Kitezh World Arks after being pursued by the lead faction of the Second Jove Empire, the “Tyrants” - whom the Triglav call their “Ancient Enemy Azdaja”. The Triglav are also very likely Jove in origin themselves.
Over their time in the Abyss, the Triglav civilization took the form of a trio of “Clades”: Perun, Veles, and Svarog - each comprising many Subclades. These groups are all fiercely individual, and often come into conflict with each other in various ways in an eternal forward-winnowing of “Cladistic Proving”; however, they are (for the most part) also willing to put aside their differences for the greater good of their race.
The concept of “proving” seems to have evolved as a necessity in the very harsh environment of the Abyss. It’s a profoundly Darwinist take on things, where every option within a subject is proven against the others to determine the superior candidate. This includes the best ways of doing things, the proper policies, the superior groups, people, technology, really anything - there is no room for relaxing in the Abyss.
Speaking of which, it also seems that the Triglav were perhaps in fact unable to leave the Abyss until recently, or at least near-completely so. So far as they knew, they were safe there - but then Rogue Drones began to get in, and then the Drifters - a group that has emerged from the ruins of the Sleeper civilization and claimed the mantle of the Tyrants, dubbing themselves the “Vigilant Tyrannos” and seeking to restore what they see as the glory the Jove race once attained in the Second Empire - entered the Abyss to chase the Triglav once more, who then responded by beginning their actions leading to today’s invasions.
The Invasion’s final purpose appears to be to re-establish a foothold for the Triglav in K-space, which they call the “Ancient Domains” - allowing them space to return to New Eden and to prepare to presumably take the fight to their rivals, the Drifters. As for the stars, they seem to be the key to a real return: Blue stars, the main target of the Triglav, produce Isogen-5 - a material that is responsible for ALL of the weird spacetime shenanigans we’ve seen in New Eden. I’m very curious to see where things go.
As for whether you should help them @Victoria_RavenSeer, that takes consideration of some things; the Triglav are against the Drifters, and reject the very nature of Sansha’s Nation’s existence - as the slave implants they employ somehow directly inferferes with their own race’s unique take on life. The Triglav are invading New Eden, but they definitely aren’t being set up as a big bad empire - rather, it seems more likely that they’re moving to become a fifth main empire themselves.