The Wayward Isle is a cluster of free-floating islands that appeared within the Wildspace of an Aetherium-controlled sphere in the year 1490 DR. The islands are inhabited primarily by a tribal nation of tabaxi, who (until recently) had not known their islands had been transported across space; they referred to the event as “the Day the Sky Changed.”
The Seekers of the Aetherium were secretly studying the tabaxi, in order to deduce the origin of the islands without exposing the groundling culture to outside influences. Adventurers sent by the Zjalans in 1491 DR delivered a spelljamming helm to the tabaxi, along with instructions for how to build a spelljammer. The tabaxi now possess the ability to enter space, and the Aetherium has ceased their clandestine research. As a result of the incident, the Zjalans were expelled from the Aetherium.
It is currently theorized that the Wayward Isle originated on Rythea and was flung from Brightspace to its current location when an Ether Cyclone swallowed the land of Lorica in 1490 DR.