Mythos was a game planned by Origin to be developed using the Ultima VI engine, with a setting inspired by historical and mythological tales of Caribbean pirates, legends from Greece, and other ancient lands. It is briefly discussed in the first edition of The Official Book of Ultima; a revision in the book's second edition omits this mention to accommodate the intervening release of Savage Empire and Martian Dreams.
Though evidently having never progressed beyond its conceptual stage in 1990, Mythos may be considered a precursor to the Worlds of Ultima games created soon thereafter, using the same developmental framework provided by the Ultima VI engine. The second and ultimately final installment of this series, Martian Dreams, was directed by Jeff George.
George would go on to serve as the first producer of what came to be Ultima VII Part Two. Under his brief tenure, the game was conceived by him and Richard Garriott as a spin-off in the vein of the Worlds of Ultima titles and Mythos before them, using the existing Ultima VII engine and taking place in a pirate-themed setting underscored by a conflict between Britannian and Vodun magic. With its early modern Caribbean influences, it is possible this early iteration of Serpent Isle evolved from concepts originally drafted for Mythos, before George's departure from Origin resulted in Warren Spector taking over the project with the premise of the final game.
- Addams, Shay. "What's to Come". The Official Book of Ultima - First Edition. COMPUTE Publications: 1990. Page 89.
- Addams, Shay. "What's to Come". The Official Book of Ultima - Second Edition. COMPUTE Publications: 1992. Page 88.
- Ray, Sheri Graner. "20 years and counting – Origin Systems". FEM IRL. Retrieved 2011-08-16.
- Armintrout, Bill. "Bill Armintrout on the original Serpent Isle". Ultima Aiera. Retrieved 2011-08-16.