The Ultraverse was the default setting of Malibu Comics' major series, a world in which a myterious Entity on the Moon (the core of a crashed interdimensional spacecraft) sent out bursts of energy called the "Jumpstart" effect, which gave certain people superhuman powers. These beings came to be known as Ultras, the most popular and well-known of which was Ultraforce. The other sources of super-powers in the Ultraverse were magic, the nanotech "wetware" developed by the hidden civilization of the underground-dwelling Fire People, or simply from being an alien from another planet or universe. Scientific analysis of these Ultras allowed some of these aspects to be artificially copied or genetically spliced into various human beings.
Behind the Scenes
The Ultraverse was fairly successful at first, even producing a short-lived Ultraforce cartoon TV series. But when Marvel Comics bought out Malibu, the Ultraverse was radically redesigned. In the event that would come to be known as "Black September" (or B.S., to most fans) the entire continuity was rebooted. Some characters where changed or retconned out of existence, many series were cancelled, and (big surprise) heroes visiting from the Marvel Universe came to dominate the remaining books. After a year and a half of this situation, Marvel finally closed down the whole company.
The Marvel Multiverse earth designation is Earth-93060.
The posible revival of the Ultraverse and their characters has been reapetidly denied by Marvel executives. Joe Quesada explained that the initial structure of the deal made "next to impossible to go back and publish these books".