Arcturus Rann is an explorer, adventurer, and living legend within the Microverse. An ancestor of Wayfinder, the man who first created and populated the Microverse, Rann was raised as the only son of Homeworld's magistrates, Lord Dallan and Lady Sepsis. Arcturus accepted the challenge to become Homeworld's first "Micronaut" (space farer) to explore the far reaches of the Microverse with a message of peace. While in suspended animation for 1,000 years (aided by his roboid companion, Biotron), Rann telepathically visited countless worlds. Meanwhile, Rann's former mentor, Baron Karza, killed Rann's parents and seized control of Homeworld. When Arcturus returned to Homeworld, he was arrested by Karza's soldiers where he joined forces with the Insectivorid, Bug, the crown-prince of planet Spartak, Acroyear, Homeworld's princess, Mari ("Marionette") and her roboid, Microtron. Together, as the Micronauts, they shared many adventures both in the Microverse and traveling across the Spacewall barrier to Earth. Rann and the Micronauts team eventually defeated Baron Karza, but not until the Baron enacted a complete genocide across all of Homeworld. Rann and the Micronauts, ultimately sacrificed their lives becoming Prime Beings, seeding life across Homeworld and restoring the planet to its natural state.
Through unrevealed means, Rann, Bug, and Marionette have been reborn, and continue to share adventures together as the Microns.