Angels, called also Philosopher Stones^{Red Imagines}, are basically parasitic worlds - eldritch beings able to subsume entire universe and freely rewrite its laws through altering its Poiesis and Logos (which are basically source codes of reality and correspond with Kabbalistic Briah and Yetzirah). They are scary alien creatures, that unlike humans know no doubt nor uncertainty, as they achieved phase of Perfect Self. Angels usually lack physical body, though they can assume any material shape they want.

The visually closest thing to angels how angels are usually presented in fiction are Wisemen^{Yellow Chrysalides}, who are basically immature versions of actual angels, though in contrast to their "adult" counterparts they actually have physical bodies. In a nutshell Wiseman is an alchemist (or other theurge), who "cuts oneself from the world". Remember Tower of Babel from Bible? It's something like that. Alchemist completely loses any ability to communicate with other beings. It's a stage of solitude and discovery of the Self. In this stage alchemist also changes physically, since he or she gains halo and fractalized wings made of virtual matter.

And last but not least, there are also Homunculi^{Orange Exuviae}, who are my take on fallen angels. It's a stage of alchemists forever stuck in the stage between Wiseman and angel, who suffered ego-death upon meeting their Choronzon/Anti-Self. To put it into simple words alchemist is +1, while their Choronzon is -1, so upon meeting both selves should logically annihilate each other resulting in 0 and an empty shell called Homunculus. Trapped in neverending loneliness and insanity, Homunculi are unable to convey any message to other beings forever. You can imagine them as grotesquely misshapen fetuses with facial features scattered randomly across surface of their skins and gross, tentacle-like wings springing from their backs. Here you can find visuals and more info about them.