Worlds of Ultima is a short-lived spin-off series from the Ultima franchise. The developers at Origin Systems envisioned the series as an expedient way of developing games using the existing engines developed for the core Ultima games.
The premise of the series is that the Orb of the Moon, the magical stone which the Avatar uses to travel from Earth to Britannia, can also open moongate portals to other worlds and time periods. Two games were released, both running on the Ultima VI engine. The Savage Empire features the Avatar exploring a land where dinosaurs live alongside tribal humans, a tale inspired by Aurthur Conan Doyle's The Lost World. Martian Dreams finds the Avatar transported to the Victorian Era, in a world where humans have traveled to Mars and discovered the remnants of a Martian civilization; this story was inspired by the works of Jules Verne and Percival Lowell.
Other Worlds of Ultima games were conceived but never fully produced, with one reportedly themed around Arthurian legends. Another, inspired by ancient Greek mythology, eventually formed the loose basis for Ultima VIII: Pagan's story, with Pagan's Titans replacing the Greek pantheon.
Both Worlds of Ultima games prominently feature the character Dr. Johann Spector, the alter ego of series producer Warren Spector (in the same sense that Lord British is the alter ego of Richard Garriott.) They are the only Ultima games in which the character appears.