Adam Kane
Adam is the strategist, tactician and moral center of Mutant X. It was his experiments that inadvertently created the hundreds of New Mutants. It is now his responsibility to save these innocent victims of society. It can be argued that he may be the smartest man alive, but he is not a mutant. It is revealed in the series finale that Adam is a clone of the founder of the Dominion.
Brennan Mulwray
Brennan is an Electrical Elemental who can generate extraordinary amounts of electricity and control its direction and flow. His energy blasts are usually referred to as 'Tesla Coils'. His primary weakness is water. His secondary mutation allowed him to charge up his electrical powers into powerful energy jets from his palms, which if fired downward, could launch him high into the air.
Emma deLauro
Emma is a Telepath, a psionic mutant. She is able to read the emotions and feelings of others, alter them and broadcast her own emotions. Her secondary mutation gave her psionic blasts that she could fire from her forehead at her opponents, knocking them unconscious, erasing memories or even killing them upon impact. Her powers expanded in range and scale as Season 2 progressed, allowing her to broadcast emotions to a much wider range, though she couldn't isolate targets when doing this. She could also shoot psionic starbursts and psionic shockwaves. Emma died in the explosion at Naxcon (Nick Fox's company).
Jesse Kilmartin
Jesse has the ability to alter his body's density, enabling him to pass through walls or to become as completely solid as stone. He is limited to about 30 seconds as an intangible state (or else risk not being able to reintegrate) and can only stay supersolid for as long as he can hold his breath. As a result of his secondary mutation, his powers were augmented so that he could also make any object he touched intangible or as supersolid as he was, allowing others to pass through the object or be as invulnerable as he was. Though he initially was seen fighting in supersolid state, he eventually seemed to be less mobile in that form, perhaps due to the fact he increased his mass hugely. Jesse is the only known New Mutant to have surpassed his "expiration date".
Lexa Pierce
Lexa was the first member of the original Mutant X but was unknown until Emma's death and Adam's disappearance. Has also worked for Eckhart at Genomex and the GSA and then for the Dominion before rejoining Mutant X. Lexa is a Chromatic and can bend light around her to become invisible, project flashes of light to momentarily blind others and focus light into laser beams which she can shoot from her fingers. After Emma died during the start of the show's third season, Lexa joins the team and sets herself up as the new leader. She did this at the behest of a mysterious organization which was secretly manipulating everything within the lives of the Mutant X team for their own reasons. Although many times disgusted over their orders for her, Lexa was forced to comply, as she believed they held vital information to the whereabouts of her long-lost twin brother. Eventually, Lexa had to kill her brother after his powers went out of control.
Shalimar Fox
Shalimar possesses both human and feline DNA, giving her the strength, speed and cunning of a jungle cat. She is a panther-like Feral who has the most common feral weakness, a fear of fire. She overcame that fear when a mutant was trapped. Her Feral abilities were enhanced during a 'secondary mutation' within her genes during the show's first season, giving her superhuman strong senses.