Biology

Skrulls are approximately the same height and weight as a normal human. Their defining physical characteristics in their native forms are their green skin color, longer ears, and their distinctive chin shape. Skrulls are typically stronger than a normal human, and also have the innate ability to change their shape and color at will.

The Skrull shape-shifting ability gives them the ability to take on the appearance of other life forms as well as inanimate objects. Often using this ability to take the form of other organisms, Skrulls can change their color and appearance, augment the number of limbs they have, and can augment their size growing either larger or smaller when needed. Concentration is needed to achieve a new form, and continued effort (although generally minimal) is needed to retain a different form. If a Skrull is injured quickly their concentration may break, reverting them back to their original form. The ability to alter their form at will makes Skrulls ideal for infiltration and espionage, and historically they are known to use their abilities a lot for deception. When used offensively, this ability is also often used for growing fangs, claws, and creating melee weapons from their limbs such as weapons for bludgeoning and blades. Skilled Skrulls can also generate wings when needed. The malleable and unstable nature of a Skrull's body can also be used defensively, even subconsciously. For instance, a Skrull's body may shift vital organs to different areas of the body when they are attacked in order to prevent fatal damage even when they are unconscious. They are also heal quickly by reforming their bodies, even from damage that may kill a human.

While Skrulls have various innate abilities due to their unique physiology, they also use their technology to augment members of their race giving them additional powers and abilities. The main types of augmented skrulls are Super Skrulls and Warskrulls.

Super Skrulls

Kl'rt the Super Skrull

Super Skrulls are genetically enhanced to give them all of the powers of the Fantastic Four along with their own unique physical traits and abilities. This means that they have the elasticity of Mr. Fantastic, the ability to generate and engulf themselves in flame like the Human Torch, can turn themselves and other items invisible as well as generate force fields like the Invisible Woman, and can turn their body into thick, craggy orange rock like the Thing. They can use these abilities individually, or any combination of (including none) at once. Different powers can also be used only on certain portions of their bodies such as using one ability on one limb and another on a different (again, in any combination of these four powers). When used offensively, these powers are often used in such a manner where different abilities are manifested on different portions of the body (some in a combination) depending on what the situation requires. All of the powers manifested by the a Super Skrull are more powerful than those that the members of the Fantastic Four possess. These powers can also be augmented by a device located on the Skrull home-world which sends a beam to the Super Skrull which can amplify his already great powers.

The original, Super-Skrull, was created by the Skrull Emperor Dorrek for the purpose of revenge on the Fantastic Four. The Fantastic Four are long standing enemies of the Skrulls, and have foiled Skrull plans for domination/destruction of Earth on numerous occasions. In addition to enhanced powers of the Fantastic Four, Skrull shape-shifting abilities, and the Skrull ray designed to enhance his powers Kl'rt was also given some limited telepathic abilities that allow him to hypnotize opponents.

Other Super Skrulls: Xavin.

Warskrulls

Warskrulls are Skrulls that are genetically enhanced to give them the ability to mimic an entity's powers as well as their appearance. One example of this was a Warskrull that copied both Professor X's telepathy as well as his appearance in order to infiltrate the X-Men and launch an attack on the Shi'ar.

Secret Invasion

In April of 2008, Marvel is having a Civil War-sized event known as Secret Invasion in which Skrulls come to earth and impersonate celebrities, politicians and even super-heroes. The tag line for the event is "Who do you trust?"

Alternate Universes

MC2

Earth-982: the Skrullian Genetechs created an Apox, a cyborg skrull capable of harnessing and using the Power Cosmic.