Primal Forms

Primal Forms are a new type of transformation introduced in Ben 10: Omnitrix Unlimited.

Overview
Primal Forms exist so far only in the Antimatter Universe, with the Schimation shapeshifter Bain Ten'eeson being the only one who can access them.

Due to his unstable genetic code, Bain is able to "unlock" dormant genes in many of his alien forms, that had been "turned off" during the species' evolution.

Essentially, the alien transformations will regress to an earlier stage of their evolutionary path, radically changing their appearance and powerset to a degree. Common traits found in many alien forms are a larger and more intimidating appearance, bigger teeth and claws, more aggressive and lethal powers, along with reduced intelligence. However, there are some exceptions, with aliens having some of their abilities actually being underdeveloped or not at all and supplemented by a different ability, intelligence remaining roughly the same and a smaller size.

An alien transformation will remain in its Primal Form for approximately 10 minutes, before Bain is impaired by fatigue and it evolves back to its normal form.

Trivia

 * The concept was inspired by the Primal Regression forms introduced in Pokémon Omega Ruby and Pokémon Alpha Sapphire.
 * Primal Forms tend to have more animalistic tendencies, displaying predatory behavior.
 * Primal Forms are the Antimatter Universe equivalent to the Ultimate Forms.