Once upon a time, thousands of years before the Terran discovery of the Shivans, there lived a species called Ancients.
These Ancients had a mind far more advanced than humans, even than Vasudans. Because of their intelligence, they began to expand their empire across the Cosmos - billions of lightyears across - and then they got too far. They got too powerful.
The Vasudans were just part of their empire - they were continously harassed, and discriminated by racist Ancients.
But, this was too much; a hidden race - almost a trillion lightyears away from GTVA space - was discovered. As the Ancients bring up another wave of vessels to conquer them, a great war began - a war that lasted probably hundreds, or even thousands of years.
This race was called the Shivans. The Shivans' minds were a fusion of Biology and Mechanics - they had a brain programmed to utterly defend themselves. The Ancient race was too much of an annoyance - the Shivans constructed hundreds of ships, each probably even more powerful than a Sathanas - to wipe out their enemies. A preemptive strike followed - the Shivans were to completely destroy the Ancients. The Shivans grew TOO powerful - and even the innocent races, once conquered by the Ancients; were massacred, and all except the Vasudans became extinct. The Shivans succeeded.
The Ancients were no more.
Now we move on to 2300. Everything is normal in Terran space - except the Terran-Vasudan War. After this 14 year war, the Shivans returned - to waste about the last of their "enemies" - the Vasudans. The Shivans weren't interested in any alliances - if they were, they'd ally the Terrans. But the Shivan mind was programmed to destroy any race that seems harmful to them.
The Terran-Vasudan alliance was formed. The Shivans sent one of their prominent monsters - classified the "Lucifer" by the Terrans - to destroy the GTA and PVA. But the Terran-Vasudan alliance was too powerful - and they managed to destroy the Lucifer.
The destruction of the Lucifer forced the Shivans to retreat and rearm. Meanwhile, there were rebels who fought for their own good - the Hammer of Light, and the Neo-Terran Front.
However, the Shivans weren't even shaken. Hundreds of fighters and bombers lurked in the mysterious Gamma Draconis nebula, headed by a beast that overshadows newcomers - the Ravana. The Ravana is massive, and acts as a semiLucifer and took out two important corvettes.
Operation "Slaying Ravana" ensued, and the Ravana was destroyed. However, the GTVA is constructing something much more massive - larger than anything Terrans know the Shivans constructed - the 20,000 foot GTVA Colossus. This monster overthrow Bosch and his faction, as well as several Shivan destroyers. However, the Shivans had deployed an equal threat - the Sathanas.
There were 90 that invaded GTVA space. These 90 detonated Capella. No one can fathom how or why the Shivans destroyed the Capella star, but it seems that the Shivans did it to threaten the GTVA, much like how the Americans dropped two Nuclear Bombs in Japan back in World War II. The Sathanas fleet is probably merely only part of the entire Shivan empire.
There seems to be alot of Shivan subspecies, there may be workers, soldiers, even queens - the soldiers were the most prominent - I guess they were the ones who withstood waves of advanced laser rifle shots.
As of now, I can only use one quote to describe them; they are elements found in Heaven and Earth that we cannot dream of in our humble philosophy.