The Skrull race originated on the planet Skrullos, Drox system, Andromeda Galaxy hundreds of millions of years ago. Although basically reptilian, Skrulls share certain characteristics with mammals. They have hair and, despite the fact that young Skrulls hatch from eggs, mothers nurse their children to provide nourishment. They live an average of 210 years and are often slightly smaller than humans. Skrulls are about as strong as humans of similar size.
Early in the evolution of the Skrull race, the star-faring race of genetic engineers known as Celestials visited Skrullos. The Celestials experimented upon the race, creating three different types of Skrulls. They bestowed a series of longevity genes upon one group, creating a race of Skrullian Eternals (equivalent to Earth's Eternals). On the second group, they implanted a latent gene series that would promote rapid benevolent mutation when the race matured. Finally, with the third group, the Celestials created a race of Deviants (equivalent to Earth's Deviants).
The Deviants developed shapechanging ability. Using its ability to change shapes, the Deviant race soon dominated the planet. It eventually eradicated the other two Skrull races. The Deviant Skrulls then turned their attention inward. It is unclear whether the Celestials created two types of Deviants, or whether the Deviant race evolved into two separate races. In any case, part of the Deviant race changed into a horrible, sorcerous offshoot called the Dire Wraiths. The "normal" Deviant majority soon attempted to eradicate the Dire Wraiths, but the Wraiths used their sorcery to flee to the Dark Nebula.
After developing interstellar travel, the Skrulls used their shape-shifting powers to establish a galaxy-wide empire. Although extremely imperialistic, the Skrulls were not militaristic, and based their empire on trade. Their shape-shifting powers allowed them to foster bonds of affection and trust with their trading partners. Where this failed, their shape-shifting powers aided them in infiltrating and undermining opposition.
About 10 million years ago, the Skrulls ventured into the Greater Magellanic Cloud and encountered the Kree. The details of this meeting are described in the Kree section. Here, let us just say that the Skrulls soon found themselves embroiled in a vast interstellar war. In order to survive, the Skrulls quickly developed a ruthless, militaristic culture that lauded deviousness and aggressiveness as much as their previous culture had praised business sense and hard bargaining. This war has raged for millions of years now without any significant peace.
Thousands of years ago, Skrull scientists created the first Cosmic Cube, which could transform thoughts into reality. The powerhungry emperor used it to expand his personal influence and holdings throughout the empire. Years later, the Cube developed a consciousness of its own. Unfortunately, the Cube patterned its personality on that of the power-hungry emperor. It destroyed two-thirds of the Skrull empire before realizing it had made a mistake.
The Skrulls patiently rebuilt and continued their long war with the Kree. Not so long ago, a would-be Skrull ruler set off a genetic bomb that destroyed the shape-shifting powers of all Skrulls. Every Skrull became permanently trapped in the form he occupied at the moment of detonation. Aside from leaving an untold number of Skrull spies trapped in alien body configurations, the genetic bomb cast the Skrull empire into anarchy. A half-dozen rival planetary rulers have claimed the lmperial throne. The empire has been forced to divert a sizeable portion of its war resources to settling internal disputes. Only the fact that the Kree empire followed the Skrulls into anarchy shortly after learning of their enemy's weakness has saved the Skrulls.
After some time the empire of the Skrulls was restored. Not long after this the latest herald of Galactus, Nova, led her master to the Skrullian throneworld. The Skrulls tried to fight Galactus with all their might but naturally to no avail. The Skrullian Throneworld was utterly destroyed. This plunged the Skrulls into chaos again. But the Skrulls also overcame these problems under the guidance of their new empress S'Byll. Just after she had became empress of the Skrulls they were attacked by the alien race known as the Badoon who were secretly aided by the Kree. S'Byll tricked the Silver Surfer into joining them and the Kree retalliated by attacking the Surfer's homeworld Zenn-La. Silver Surfer and S'Byll with her fleet followed the Kree to Zenn-La but they were soon overmatched. Then S'Byll consort Kl'rt the Super Skrull convinced Silver Surfer to use his cosmic powers to restore S'Byll shapeshifting powers and the allow her to do the same to the other Skrulls. Zenn-La forces joined the Skrull and Silver Surfer but the battla wasn't ended before Silver Surfer forced an audience with Nenora, supreme leader of the Kree, if he would leave Zenn-La forever the Kree would abandon their attack.The Surfer left and the Kree and Skrullian forces returned home. The Skrull to the homeworld of S'Byll, the new throneworld Satriana. There S'Byll has begon restoring the shapechanging powers to loyal followers.
After many internal struggles against rival claimants to the throne S'Byll once agian ran into the Kree. When treachery cost them their military leader the Skrull were soon defeated. Only S'Byll survived by using her shapechanging powers. Because Nenora had kidnapped Shalla Bal, empress of Zenn-La, because she had found out that Nenora was actually a Skrullian spy who had wanted to build her own empire, the Silver Surfer and S'Byll agreed to attack Hala, the Kree homeworld, themselves. The invaded the palace of Nenora who then was killed by S'Byll. The Kree were gratefull for the uncovering of the treachery and agreed to a truce with S'Byll that would allow her to rebuild her forces.
Even more recently Skrull agents, knowingly or unknowingly working for the Kree Supreme Intelligence, were instrumental in starting the Kree-Shi'ar war. What exactly was their purpose in unknown although they could have been paid or controlled by the Supreme Intelligence.
Notes on the Skrull Empire and their planets:
The Skrull empire is located in the Andromeda Galaxy M31 which is located at a distance of approximately 650 kpc (kiloparsec). Their current throneworld is named Satriana.
There is a lot less known about the planets of which the Skrull empire consists but since it is located in a Galaxy about the size of our own it's probably considerable, although it's not certain that at each of these planets S'Byll's rulership is acknowledged.
Since it is known that the Skrulls are able to breath in Earth atmosphere but are a bit weaker then the Earthlings it is probable that most planets of the Skrull empire have an atmosphere of about the same composition as Earth but the gravity will be somewhat less.
- Shape Changing: Typical (those whose powers have returned thanks to S'Byll).
Source: Marvel RPG and more