Yami transforming her hair into dragon heads with Transform.
Body Transformation, or simply Transform, is the fourth Path that was meant to be passed down by Nemesis, but instead she used it to form an organization of assassins, that allows the user to transform any part of their body to virtually anything.
Generations
See also: Nemesis' Organization
As the original user of Transform, Nemesis is the only one who is capable of using Transform to the fullest. Wanting to use her abilities for her own personal gain instead of sharing it, she formed an unnamed organization that consists of aliens she had born from science labs and trained as assassins for hire. Using cell plantation, Nemesis inserted her own cells into the "creations" that was enough for them to develop traits of hers, notably Transform.
First Generation
The first wave of Nemesis' creations are known as "first generation weapons," and Yami is the only person to have survived this generation as it was the most experimental. Yami has displayed enhanced strength, speed, reflexes, etc. like all aliens, but also basic handling over Transform.
For battle, she is able to transform her limbs into or extend off of them blades, wrecking balls, claws, etc., and shape clumps of her hair into dragon heads, fists, etc. Otherwise, she is able to change her appearance (i.e., once she has debated whether or not to increase the size of her breasts) and outfit (similar to Dressform).
As Yami only holds a small amount of Nemesis' cells in her body, the duration and extent to which she can use Transform is limited compared to other users. But considering her success as an assassin, Yami seldom has faced a situation where any limitations of hers has proven to be a problem.
Second Generation
Nemesis' only other wave of creations are known as "second generation weapons," and Mea is the only one. Whether or not Mea always made up the entire second generation or if she is just the only one who survived, there are no other known second generation weapons.
As a second generation weapon, Mea was given a higher amount of Nemesis' cells than Yami during her creation. This not only allowed Mea to develop Transform even further than Yami has, but is apparently also the reason for Mea's connection with and undeniable loyalty towards Nemesis.
Mea connects her mind with Rito with Transform, controlling him to pleasure herself and shares the experience with him.
For battle, in addition to all of what we know Yami can do, Mea can extend off of her body much larger-scale weapons, mainly blades, as well as energy cannons. Perhaps the greatest difference between first generation weapons and second generation weapons, Mea can use Transform to connect her mind with other people. With a single touch of her hair to their spinal cord, she can enter that person's dreams, access their memories, etc. and also share with them whatever she's currently feeling to a limited degree (i.e., sexual pleasure). As long as the victim is significantly weaker than Mea, she can even control them for a certain amount of time.
Original Generation
Nemesis makes up the entire orginal generation, as she is the first person to develop Transform at all, and the only person who is capable of developing it fully, which she has.
She has access to all of Yami and Mea's abilities, in addition to her own. Besides complete mastery over all Transform abilities, Nemesis is able to transform herself far beyond how Yami and Mea can and change her age. As a means of immortality, Nemesis can be any age she wants for as long as she wants, favoring youthfulness. Her exact age is unknown, but it's presumably close to that of Madara's.