Welcome to the convenient sketchbook guide to the universes of Ann S Koi.
I. What are these things?
The easy answer is, "Angels". 'But they have tentacles! Angels don't have tentacles!' Actually, there's a global mythological precedent for god-forms with amphibious features.
Old Persian art rarely if ever depicts angels with feet; the wings cover most of the body. This art was probably the inspiration for descriptions of angels in the Bible.
Seraphim were described in the book of Isaiah (6:1) as having six wings: "with two he covered his face, with two he covered his feet, and with two he flew". If his "feet" were covered, who's to say they were feet at all?
Descriptions of Cherubim, such as those in Ezekiel, are those of multi-faced monsters with what appear to be long, straight legs ending in hooves like a calf. The Cherubim were said to be bathed in fire, glowing radiantly, and moving at high speeds, as well, so this partially glimpsed celestial creatures may well have had any sort of appendages. The gentleman in charge of documenting this vision may also have lacked a context for "fins" or "tentacles", particularly on something flying through the air trailing flames. (The description of Cherubim gets even stranger as it details the flying, intersecting wheels full of eyes which accompany the creatures. Can't say if this indicates particularly good drugs or an early record of alien invasion.) Please note also that when the glory of the LORD is witnessed in the same chapter, the figure is only described as having the shape of a man, and only really detailed from the waist up.
See Truthseeker for an example of a particularly monstrous angel.
Islamic angels were described as shape-shifters who chose the forms of men to interact with men, presumably to make communication easier (it's tough to get a message across when the audience is running in terror).
Other folkloric and occult traditions describe angels as beings of pure light or shifting energy, or variable in appearance depending on who was witnessing. In the Baha'i faith, for example, an angel is the highest form of evolution for a human soul - one supposes that one might choose one's own form at that point, no?
In spite of any aggravating pop culture connotations the word may have recently acquired, the artist is rather fond of the Hindu term, avataras, which is used to describe incarnations of various gods. In many cases, the artist uses an aether angel or an elf-like being to represent a commonality found in multiple god-forms across a variety of mythos. It is fine to view them as either fusions or distillations, with each embodying aspects of the complete human existence (an emotional state, a desire, a fear, etc). The term egregore, an occult term referring to a collective thought-form, may also be used to describe many of the aether angels.
The star angel illustrated above is a skilled shape shifter (but not yet a master); "he" has managed to manifest both feet and genitals by sacrificing a distinct face and mouth. You may see him materializing from the aether, in color here.
Next: Part II, Ecology of the Aether Angels
Ann Koi Gallery