The Skornn is a member of a vicious ancient alien or demonic race also known as Skornn. At some point in time they encountered the Shi'ar Empire. On Earth, the Skornn terrorized Macedonia and other areas between periods of slumber, feasting on the energy signatures of the few mutants they could find. During one such slumber, a group of powerful mutants, including En Sabah Nur (later Apocalypse) and Garbha Hsien (later Saul), created the Five Fingers of Annihilation blade to destroy the Skornn. Later, in the city of Karanada, the local priest threatened to awaken the Skornn, prompting the council of Nirinthia to seek out the Traveler (Nathan Summers, later Cable), for aid. His arrival came to late, upon his arrival he found that the entire town including the council priest had been slain. The mutant priestess D'Narda was the only survivor, together they defeated the Skornn, but to do so D'Narda had to sacrifice her life.
Years later, in present time, the Helix wanted to recreate their master. The plot succeeded when they managed to rob the sword known as the Five Fingers of Annihilation from the mutant Shatterstar. With this battle resulting in the death of some of Shatterstar's friends, he and Cable enlisted the aid of their former team, X-Force.
Alongside the aid of Deadpool, Wolverine, the Fantastic Four and a new (futuristic) Incarnation of the Mutant Liberation Front, the mutants and heroes eventually managed to kill the Skornn. At first, it even seemed that Cable had sacrificed his life to end the battle, but he reappeared not too long afterward. With Cable's reappearance, it isn't completely certain if the Skornn is dead or not, and he is just waiting on the right moment to return. But for now, the Skornn is history.