Ultima Thule: 6.2 Addition

[Cleretic]

If people want visual reference for where it is: it's a little to the left of the gloopy thing in the skybox; it can be positioned behind the landmass that looks like it has the 2300AD domes from Chrono Trigger. Interestingly, it doesn't seem to be a literal skybox element like said gloopy thing or the Cocoon or Holy Materia lookalikes, it's physically present.

It's also not there until very specifically you complete the Stigma Dreamscape, so yeah, it's a near 100% certainty it's related to the Omicrons. (You can make it disappear by NG+-ing to a point in Endwalker's story.) They do tend to add the zone elements the tribes need in the major patch before the minor patch that introduces the tribe itself.