For primary sources consult The Temple by HPL.
General Correspondences (stars are best guesses):
Epithets: The Laureled One
enn: Hardaes Gloon Ensayes Hah
Time of day: night, dawn, the afternoon
colors: silver, sea blue, ivory/white, possibly green, black, and gold
Materia: ivory, sea-stone. any gemstones from the sea, perhaps obsidian.
Symbols/themes: sunken ships, underground cities, false light, Hellenism, art (stonework), curses, communication, violence, condemnation, paranoia and delusion, [TW] suicide
power over the dead/resurrection, embodiment, reality bending, the depths of the unconscious.
Genealogy: I do not know in all honesty. i think the idea of him being a child of Umr-At-Tawil might hold some merit considering the laurel in the ivory image and the false light created by his... underwater temple. as well as the "purity" and "condemnation" talked about by the sailors. Nyarlathotep could perhaps be equal in this regard considering he more easily effects people with more spiritual persuasions or more percepetive/inuitive people, and how easily Gloon interrupts the ship's communications and function of the ship itself.
I think Gloon works by... bending perceptions and causing madness, and possibly having power over the dead. I think he is very powerful in this regard. He could be regarded as a psychopompic deity as well, somewhat.