Ultima Online is the product of Richard Garriott's idea for a fantasy game involving several thousand people who can all play in a shared fantasy world. It is responsible for grandfathering the genre of the MMO, and showing the industry that MMO's were the next era of gaming.

During the earliest span of the age of darkness; found in the writings of only the most aged of manuscripts, lived a world born of mystic arts and ancient sorcery: Sosaria. Despite Sosaria's enchanted origins, it's people shunned magic, for it's very use corrupted the souls of the unwary. But one man dared to awake the slumbering powers of Alchemy. Twisting the awesome power of the Gem of Immortality to his will, and binding all of Sosaria to his corruption: Mondain the Wizard. His power was absolute, as the whole of the planet was gripped in his cruel embrace. Only the appearance of a stranger saved Sosaria from impending destruction. From whence he came, no one knows; but his strength and his courage were without peer. In this stranger, lied Sosaria's only hope; Only a traveler from the stars could release this world from Mondain's vile stranglehold. He would prove himself a savior; shattering the Gem of Immortality, and defeating Mondain. But... A deeper and more sinister evil was released with the destruction of the Gem; For Sosaria was not free of the stone's power. O planeta ainda estava preso à magia da Joia, mesmo quando ela estava quebrada no chão do Castelo de Mondain. Pois dentro de cada remanescente despedaçado da joia, vivia uma semelhança perfeita de Sosaria... Assim é o mundo em que você nasce, vive e morre. A Britânia, que já foi Sosaria, agora existe como mil mundos; cada um com seus próprios povos, história e destino. Este Britannia é apenas um dos muitos, no multiverso que é: Ultima Online.