Gonna copy-paste the info I typed up a couple years ago:
They're a mass of beings that managed to fully colonize and "perfect" their universe. Satisfied, they're now moving onto other universes (so I guess they're 9th dimensional beings, if they're going from one completely different universe to another?), hoping to either colonize and enlighten the inhabitants, or let them be if they do not wish to change their ways (mostly out of fear). Since they come from an entirely different universe, they are composed of something that is almost not affected by gravity (save for their feet, which are a very dense version of the substance and act like lightweight "anchors"). I haven't yet figured out if it's because the substance (or the light-rings/cores) directly cancels out gravity or if the substance is simply so light that even significant gravitational forces do not affect them much. So far, I've been going with the latter, but I suppose the former would allow for some cool black hole-related stuff--event horizons acting even weirder and whatnot.
About the light-rings/cores: they have four of these things (head; chest/torso; one on each "hand"), the main purpose of which deals with electrons and magnetism (or a variant on it). To move about, they use their already light weight to their advantage by propelling themselves to and fro with streams of electrons firing from the glowing circle things, though they can also fire small bits of matter (themselves) in a pinch (usually in outer space, though even then they can't move very fast or far). And about the substance they're made out of: it behaves very much like Mercury in the way it keeps itself together. It does this by surface tension and magnetism; their form itself comes from how the substance naturally wants to shape itself in accordance with holding the energy necessary for performing the functions the light-rings/"cores" do. Because of this, even when encountered with blunt trauma sufficient enough to separate parts of the being, it can draw that lost substance back, and it will naturally form back into the shape that it was. However, it can't shapeshift--though if it loses enough of the substance that it can't get back for some reason (it drifts too far away to magnetically draw back, for example) it can shrink itself to make sure it's proportionally stable. If it loses enough, the energy becomes unstable and the entire being collapses. If other beings find some of this substance, they can absorb it and become bigger, though this also causes them to become somewhat unstable and they can similarly just collapse. When they collapse, the cores disappear, and the energy goes back into the atmosphere (where it originally came from). There was a point at which these beings were manifesting, but ever since they stopped, nobody remembers how they came about. It's hypothesized that first the substance came about, then the ambient energy was attracted to it and they began to shape each other. The beings use this ambient energy to move themselves, others (magnetism), etc.
Because of how the cores sound when active, most languages have given them a name similar to "Aou", but because of the way they look and move (especially when blunt trauma is applied), English has dubbed them with the label "Mercurials". (I'll probably be using them interchangeably and inevitably I'll end up liking one better, heh.)
To communicate, they increase and decrease the energy to their cores by varying degrees of intensity, length, and abruptness. If one were to try transcribing this onto some kind of written form, it could be visualized as longer and shorter "blocks", as well as lines and squiggles. The two former are for longer abrupt starts and stops, and the latter is for gentle undulations, starts, and stops.
Ah...I worry I've made the light-rings look too much like the Portal portals, haha.