From the introduction:
Ultraverse is a fast-paced system designed to create superheroic, fantasy, science fiction and countless other types of adventures for players. Each player assumes their own role as a character in each campaign that the Gamemaster creates. Ultraverse is designed to emulate the fictional powers and abilities found in the pages of four-color comic books, the sword and sorcery powers and settings of fantasy novels and movies as well as the high-tech weapons and abilities of science fiction books and movies. Polyhedral dice such as d20, d12, d10, d8, d6 and d4 are required for play in Ultraverse. Hexagonal or Square maps are useful but not required for playing.
Ultraverse is advertised as "compatible with" d20 System, though there are some significant differences.