Still, there is much unknown about Salvene culture and other species find it hard to understand why members of such a double-dealing violent species would trust each other so easily. And there is the matter of their spectacular entry into interstellar space. They are the only known exception to the rule that the step into space is an uncertain and cautious one.
What you are about to read is the product of much speculation about little factual information, and may not be accurate.

The early history of the Salvene can be summarized quickly: They were the toughest of a tough bunch. With teeth, claw and tools they fought their way to supremacy. With single-minded determination they conquered, enslaved or destroyed all their competition on a world which provided many deadly enemies of all kinds. In the end, they had reduced the second sentient species (a race of humanoids) on their world to labor forces, and completely wiped out the third. Their slaves can even now be found on wrecks of Salvene ships, and it is for this reason that Salvene ships are fit for humanoids with only minor modifications.

Which was first, noone except the Salvene can tell, but their aggressive exploitation and religion go hand in hand. The very fact that Salvene have a religion is something few others know. If they knew what it is like, the Salvene would have a much harder time dealing with the other races. One thing is certain: No Salvene will speak to other species of holy matters. The following was gathered by telepathic interrogation of a captured Salvene. It committed suicide immediately after it found out what was going on, so the information is incomplete.

In the beginning there was only the Egg. It was all that existed, and it was complete. Inside the Egg rested the Mother-Goddess. The Egg provided her with sustenance and She grew. But She was not alone, for the Egg was complete, and so for every side of the Goddess, there was an opposite, imbedded in legion of creatures. And they fought over the food provided by the Egg. The Mother-Goddess was strong and She conquered the others one by one. But the others were devious, and they plotted to escape the Goddess' wrath. Too late did the Goddess see the evil of the others; they succeeded in causing the untimely hatching of the Egg. The insides of the Egg leaked away into the universe, and in time formed the myriad stars and planets. And so the others spread and escaped. This, the Goddess saw and she was dispirited, for she knew she could not find all the others alone.
But lo, the Goddess was wise, and chose to split herself into manifold parts. She became the Mother-Goddess, who gave birth to us. And in us she planted her last desire: that we finish her task to defeat all others, and assume rightful rulership of the universe that came from the Egg.

This religion not only fit perfectly in with their struggle for supremacy on their own world, it also prepared them for the existence of other species, and the need to fight and conquer them. Other data suggests that Salvene knowledge of space beyond their star system was extensive, long before they could gather it by observation. Exactly how they got this knowledge, we cannot say.
What we can say is that the Salvene prepared well for their conquest of space, and their first advance was almost beyond belief, certainly beyond that of the human generals opposing them. It was more a matter of luck than strategy that the Thevians, Ik-thorne AND human forces began their counter-offensive at the same time, thus forcing the Salvene to fight on several fronts, and finally halting their advance.
A kind of stalemate resulted, and slowly, the enormous resources of the three opposing resources began to weigh down on the Salvene war machine. It was at that time that a new decree came down from the religious hierarchy: The turning of the tide was a sign from the Egg that the Salvene should not make the same mistake their Mother-Goddess had made and rely on brute force only. "Cattle should not be fought. It should be milked, fatted, and slaughtered." And thus they began a program of exploitation on a scale unheard of (except by a few humans with knowledge of late 2nd millennium Earth history).
Disguising it as free trade and even participation in the 'Federation', the Salvene have embraced intrigue as a new way to victory. Experts agree that should they ever gain the upper hand again, their next bid for domination will be a matter of time.

Significant, especially to the Salvene themselves is the lack of a unified reaction from the other species. Only the Thevians and the West Quadrant Humans have openly spoken about the need for an alliance against the Salvene, which is perhaps not unsurprising, given the WQ's bad experiences with "Human" domination, and their close ties to the Thevians.
The Humans seem to have placed their bets on the Federation, ignoring the critics who point to infiltration by the Salvene. Th Creonti mostly ignore the whole subject, while the Alskant refuse to believe that peace is not an option and the Ik-Thorne ambassador, when pressed, voiced the ominous words that "the Salvene would at least be consistent in their rule".

Apart from politics and war, there is another aspect where the Salvene religion may well shed light, that of the trust between Salvene and the extreme distrust of other species. There have been many theories about this, and the (until recently) most popular stated that Salvene release pheromone-like substances which communicate a wide range of emotions and the like, including honesty or deception, making it impossible for Salvene to lie to each other. Naturally, they would not be able to ascertain the honesty of other species in the same way. This theory was refuted however after it was proven that Salvene ship communications systems do not transmit scents.
A more likely reason is simply that of shared religious fanaticism. Almost every cult and religion in recorded histories eventually fostered distrust against outsiders. The Salvene take this a step further, viewing others as dangerous offspring of "the others" at best, and as wild and unpredictable animals at worst. Nevertheless, a number of Salvene has taken their commandment of co-existing with the other species very literally, and have learned to live with, and even come to accept the others. There are very, VERY few Salvene that ever come to view others as equals. They are viewed as heretics of the worst kind. Federation records do contain a small number of extremely vicious executions of Salvene by other Salvene. Invariably, these were explained as executions of dangerous criminals, but independent authorities on Salvene culture maintain that they have no justice system, other than "might makes right".