The Skrull shapeshifters are the result of Celestial manipulation and are comparable to Earth's Deviant race. However, these Deviant came to supplant their ancestors as the dominant race of Skrulls. The Skrulls shapeshifting is cosmetic only; they cannot duplicate powers without technological assistance. Two warrior Skrulls have been modified to possess powers: The Super Skrull, with the powers of the Fanstastic Four, and Paibok, the Power Skrull, who has the powers of some of the X-Men. Lyja Lazer Fist was also modified to possess bio-blasts, but her shifting abilities are standard. Other Skrulls, most notably the ones who teamed with Apocalypse to capture the X-Men, and who were members of a force designed to infiltrate the ranks of Earth's heroes, used special technology in their costumes to mimic the powers of the heroes they copied. In addition, the Skrulls recently began breeding more of their own mutants, whereas before they would euthanize them at birth.

The Skrull Judgment

Millions of years ago, the Skrulls were an advanced race that explored the galaxies in serach of peace and knowledge, until they came to Hala, a world with two sentient races: the humanoid Kree and the plant-based Cotati. To determine which race was worthy of an alliance, the Skrulls had the races engage in a competition of creation. Whoever created the best construct on Earth's Moon would win. The Kree created a great city and enclosed it in an atmosphere. Today it is known as the Blue Area of the Moon. However, the Cotati actually terraformed their area of the Moon and made life grow there again, and were awarded the alliance. The Kree, still in a semi-barabaric culture, were enraged and slaughtered the Cotati and the Skrull delegates. The Skrulls them became embroiled in a war that spanned galaxies and lasted until a few years ago, when Rick Jones used his latent Destiny Force power to stop the fighting. Over the years, the Skrulls became more and more warlike, and became feared as great conquerors, feared both for their power and for their stealth and trickery, as they used their shape-shifting abilities ruthlessly. It is now known that the Skrulls, originally a peace-loving people, became cruel and ruthless warriors because the Kree believed them to be such. At the time when they met the Kree, the Skrulls had already entered the third stage of their Celestial mutation, which was to become that which others believed them to be. The Kree expected, even desired a fearsome foe, and the Skrulls had no choice but to become that. However, eight years ago, Galactus came to the Skrull home system and destroyed it, leaving the Skrulls who were off-world without an Empire.

Warskrulls

The X-Men have come into contact with the Skrulls twice. Once was when Deathbird had Lila Cheney transport them to the Shi'ar Galaxy, where they eventually found that Professor Xavier, the Starjammers, and the Imperial Guard had been replaced by Warskrulls, a strain of Skrulls that could duplicate the powers of mutants and other super-powered being using a template-encoding technology. The Warskrulls had hoped to use their Xavier to control Lilandra and take over the entire Empire. The X-Men stopped them, however, and the Warskrulls were rooted out and captured.

Galactus Eats Planet Skrull

The second time the X-Men met Skrulls actually started in the aforementioned destruction of the Skrull homeworld. The X-Men had accidentally been transported there from the Oktid dimension, and found that the Skrulls of that time were working with technological apparatuses to simulate the powers of Earth's super-beings, hoping to one day replace them and mount an invasion. The X-Men tried to stop Galactus from his feeding, but were unable to alter to course of history. Luckily, some Skrulls whose Terran templates had died (rendering them useless) led the X-Men to a spaceship that they used to get to Earth in eight years (programming in the right time of stasis so they wouldn't feel it). However, the Skrulls who had survived knew of the X-Men's presence and escape, and tracked their craft and intercepted it. They abducted Wolverine and turned him over to their ally Apocalypse, while replacing him with a special Skrull who had been conditioned to believe that he WAS Wolverine. Apparently, the Skrulls were hoping that Apocalypse could help them find a new homeworld. The X-Men discovered the deception when "Wolverine" was killed by Death III, and when Fiz, a mutant Skrull, defected to their side. After Apocalypse was defeated, however, the Skrulls vanished, leaving the X-Men in custody of all their technology and the mutant Skrulls who defected. Professor Xavier then took the mutant Skrulls into space to find them a new homeworld.

The Skrulls in Alternate Realities:
Mutant X: The Skrulls tried to attack Havok and Scotty Summers because they were related to the Goblin Queen, possessor of the Goblin Force (like the anti-Phoenix). They were diverted by the Watcher, who informed them that the Goblin Queen had been defeated and was no longer a factor.

Earth X: According to information gleaned from this possible future, the Skrulls had reached the third stage of Celestial evolution when they met the Kree. This caused them to be highly susceptible to the mental suggestions of those around them, and it was therefore the Kree anticipation of Skrull agression that caused the Skrulls to rapidly change from peace-loving to militaristic.

The End: Due to the rising of the Phoenix, the Warskrulls attacked the Xavier Institute and other related X-locales, posing as old friends or dead foes. Eventually they blew up the X-Mansion with a huge nuclear bomb, killing many X-Men and students.

Ultimate: In this universe, the Skrull are known as the Chitauri, and have been on Earth since the 1930s, when they helped Hitler organize that Nazi party and begin the Second World War. The Chitauri are also shape-shifters, but they must actually ingest the flesh of the entity whom they want to replicate in order to transform. They are a hive-mind species who believe it is their destiny to bring the whole universe into a universal harmonious thought paradigm. They view independent thought as a disease, and are on earth to impose their view of order. Apparently, the Chitauri are not 3-dimensional beings in their natural form and maintain their physical humanoid forms in order to interact with our world.