It is the art and science of (often speculative) abstraction which marks a "thisness" as envelope or shell of a being. Speculative imagination essentializes it on a qualitative level, and speculative reason illuminates its formal structure. Ordinary consciousness of course apprehends in most cases only accidents.
It is conceivable that there are beings which are made up only of essentialities, just as there may be beings with nothing essential in them whatsoever. It is also possible that there are many empty shells. Shell secretion is a natural function of all beings but for a few, equivalent in their structure to the modern day gastropods if relatively terrestrial, or to stellar cephalopods if their relations and non-relations are of a more speculative character. These are, it should go without saying, the formless.
Most of being passes successively from hierarchy into form, where the seeds of hierarchy exist only as a certain entailment between the essences of beings. The power of this entailment, however, cannot be overstated, and it sometimes occurs that essence becomes accident under its sway (or vice versa).
A universal is not something which exists in each being, nor is it a shell under which all beings fall (though there is such a thing, and it is pure chaos). Instead, it is a principle of entailment (we might say, artistically, a rule of derivation) which has an unrestricted domain. These probably exist in the rarefied atmosphere of the purest emanations, or perhaps in the burning passage of a stray comet. No one said such things were eternal.
Of course all this remains to be more clearly formulated, and at some point even formalized.