Previous Headmates,
A Hypothesized History
So, in our headspace, for the longest time it was simply Emby and Ghost. At some point, Ghost started getting feelings that headspace (what little we understood of it at the time, at least) was "wrong" in some way, and attempted to integrate everyone as a means to end headspace entirely. This worked on everyone but Emby, leaving the two of them stranded in a dying world. Ghost, at some point would find out the hard way that this was not sustainable, because eventually he would shatter, leading to various fragments of his personality being left in headspace.
After a while of being completely alone in headspace, Emby would attempt to create a new headmate out of some of those fragments, this being the Dunes we currently know. At around this time, fragments from Ghost would unintentionally start forming their own Dunes, who we'll refer to as oldDunes. Possibly as a side effect of this, another headmate would begin to form at the same time. This one would become System Ruby (sysRuby).
Before we explain the rest of sysRuby's history, there's a diversion we need to make. That being explaining what happened to oldDunes.
oldDunes, as we know it, would shatter in some way while leaving a new headmate behind. This new headmate is Wynd. A lot of the oldDunes fragments would sort of coalesce with the fragments sysRuby would shed overtime, making it harder to discern whether a headmate is mostly from sysRuby or oldDunes. The only real exception is Seunp and Rapids, who are very, very clearly results of oldDunes rather than sysRuby.
Back to the main topic though, sysRuby, being an amalgamation of the remaining fragments, was not very stable compared to Emby, Dunes, or oldDunes. sysRuby is thought to have been a subsystem, comprised of various headmates it would create on its own in an attempt to seem "whole" to the outside world. sysRuby would, over time, slowly shed fragments on its own. This may be the origin of Pur, but there's nothing concrete enough to prove that.
Eventually, the original Ruby (oldRuby) itself would experience something completely new to us at the time, where it seemingly had lost the ability to communicate amongst the other headmates. This would coincide with the original Biscuit (oldBiscuit) appearing occasionally, possibly fighting for the front in sysRuby. A few months later, both oldBiscuit and oldRuby would be ejected from sysRuby. sysRuby would soon be known to the others to still exist, and would take the appearance of "the system itself", seemingly mistaking its subsystem-ness to be a sign of being an embodiement of the base system.
Over time, sysRuby would shed more and more fragments of itself, which all would eventually either form into their own headmates without the others knowing, or modify currently known ones. This would lead to oldRuby and oldBiscuit seemingly swapping personalities at some point. sysRuby now goes by "Relicra", named after the three inhabitants remaining (Red, Lutalica, and Lyra) who seem to have things under control within their sisasystem.
Some Trivia:
Nearly every headmate outside of the "Edwyhpurral" group was, in some way, caused or influenced by sysRuby's collapse.
Ghost is believed to have worn a blue jacket that had dark gray stripes. This is evidenced by absolutely ANCIENT artwork of ours from 2018, which shows Ghost attempting to "attack" Emby. Below is a recent drawing of the jacket in question, drawn while we were figuring all of this out still.