Legion is an immensely powerful Omega-Level mutant suffering from Dissociative Identity Disorder, with each persona manifesting and controlling a different superhuman ability. Originally only psychic in nature, David’s powers now include physical mutants.
To date, he has displayed telepathy, telekinesis, pyrokinesis, shape-shifting, time-travel, teleportation, superhuman strength, sonic blasts, flight, a prehensile tongue, X-ray vision, super speed, inter-reality and interstellar travel, creating a field of absolute absence of heat and love, skin manipulation, healing, lycanthropy, transmutation to salt, omniscience, time control, duplicate generation upon physical contact, weapon’s mastery, emotion manipulation, pain transference (“living voodoo doll”), spirit absorption / body control, generation of armor made from various substances, teleportation to the presence of specific people rather than location and the ability to restructure all of reality. The specifications and limits of each power has never been made known or tested.
Legion is able to access the memories and knowledge of every consciousness that has taken control of his body, including the military and hand-to-hand combat training of Jermail Karami.
Using a helmet or wrist-mounted device, created by Dr. Nemesis with aid from Reed Richards and Madison Jeffries, Legion is able to choose a particular persona’s power to utilize; these devices theoretically keep the persona from claiming permanent dominance of David’s mind and body.
When his mind is whole and intact David can use any of his powers at will or even multiple powers at the same time. However, there are only a few instances when his mind has been united enough to do so, namely the times when he was possessed by the Shadow King and the time when his mind was healed after emerging from a coma at the beginning of Legion Quest.
He also wields a psychic knife that hurts mentally as he focuses on using its psychic powers. He can create psychic blasts which are comparable to concussive blasts, though attacking the minds of its target.
Legion can also convert himself into an astral form which enables him to travel through astral planes and create psychic weapons. He can also teleport and travel through time.
After the events in Colorado, the X-Men used a device to flatline David’s brainwaves to get him to San Francisco, where they began psychically sequestering and cataloguing his personas in psychic “cells” - to date, seven psychic surgeries have contained 53% of his personas. The X-Club believe once healed Legion maybe able to cause spontaneous mutations, serving as a cure for mutats whose X-gene has been dormant since “M-Day” depowered the majority of mutantkind