Not much is known about Random's past except that he really is just a young boy who can shapeshift his body into almost anything he wants. He changed himself into looking like a taught mercenary and became just that, a mercenary for hire.
Random was created by Peter David and Joe Quesada and first appeared in X-Factor issue 88 (1993).
Mayor Story Arcs
He was hired by X-Factor to help in a few missions as a reluctant ally. He developed a friendship/crush on Polaris. Later, it became apparent that Random was an agent of the Dark Beast, who used him to capture Havok. Random's true nature was also revealed, that of a young man with little control over his body's gelatinous properties who had received aid from McCoy, for which the Doctor was now demanding payment in the form of service.
Random was seen at the concentration camp of Neverland and was guessed to have died there along with the other prisoners. He later re-appeared as one of Exodus' Acolytes along with Frenzy and Tempo, but was beaten by Northstar and Aurora.
Random was shown fighting alongside many others in the last battle of the Messiah Complex.
Random was shown as a member of the Acolytes and Exodus still as their leader, when Charles Xavier goes to New Avalon. Xavier was able to convince Exodus to disband the Acolytes in order to help mutants in other ways. Random decided to relocate to San Francisco with the X-Men.
Random was seen during the siege with mostly mutants that were regularly villains, like Toad and Dragoness. Random and the former villains helped defend Utopia during Bastion's attack. Shortly after Second Coming, Random joins members of the X-Men on a volunteer mission to help rebuild San Francisco.
Brotherhood and Krakoa
When Joseph (posing as Magneto) reformed the Brotherhood of Mutants, Random was one of the members. He later appeared as a resident on Krakoa island.
Random has a form of reactive shape shifting. He can adapt to counter any powers used against him. He can also fire protoplasmic projectiles from his arms and has a degree of super-strength and invulnerability.
Random made a cameo appearance in two episodes of the 1990's X-Men animated series. One of which was Sanctuary, Part 1 (Episode 51)