After having worked on the game for two years (June 1999 to June 2001), it was cancelled as the rights to the Myst franchise transferred from Mattel to Ubisoft.
According to Fortier, Ultraworld’s development was only about 20% finished, but the designs themselves were completely done. The game was presented in realtime 3D, a first for the series at that point. Some ideas from Ultraworld even managed to carry over into Myst IV: Revelation. Specfically the inclusion of Sirrus and Achenar, the two brothers from the original Myst.
Two original characters were also featuerd in Ultraworld, Kervis and Merinia. The purpose of these characters are unknown, as is most of Ultraworld’s story. A sketch showing off an “Ice Locall” age is also featured among the concept art, showing a mechnical panel controlling some sort of platform.