I've provided links to some of the individual descriptions. Please keep in mind that I only dabble in this from time to time, and that a full-fledged Pantheon would not be published or "webbed". I don't have the time.
If you want to create something for this pantheon and see it printed here, you can always drop me a line at firstname.lastname@example.org. If I like it, and I have the room to spare (limited space, sorry), I'll print it here.
The Eld (also known as the Eldest Entities), are the first of the Deities, those who existed at the birth of the worlds. They are to the gods what the gods are to the mundane. There are only three of them, all of Greatest Rank. These beings are respected by gods and not worshiped by mortals.
EA is the first being, the one who brought order to the storms that shook the Astral Sea when the sparks of light awoke the lifeless formless mass. He was the first Sentient, the Master of Thought and Conceptuality, bringer of Time, and Master Mystic of the Quasi-Entital. Some say he is pure He is removed from all, yet intervenes to aid all. Supposedly, he created the mental energy that allowed thought, opened the powers of the Quasi-Entital planes to stabilize the cosmos and form the spheres and subordinate planes, as well as empowered the spark that created spiritual force to be strong and independent.
EA retreated back to his mysterious realms, places that are likely beyond conceptuality, but does let his thoughts be known to all when needed.
EA does not have a stable form. When EA appears, he appears as a surrealistic form, usually an altered form of a normal creature, a bizzare optical illusion, or a form that is "greater" than 3 Dimensions and envelops non-ecludian geometry. For instance, EA's appeared in visions and dreams as a humanoid with a smooth head having no eyes nose, ears or mouth on it, two floating mouths and eyes in the palms of its hands. Once he appears as a burning stone, another time as a two-dimensional dog with a cats head and a human mouth.
EA's symbol is an open Hand containing eyes on its skin. He is removed enough that he does not grant mortals spells, and has no clergy. Some few true Mystics and Savants, however, attempt to tap his energy.
Æna is "Mother Earth". She created the mundane realms and mundane spirits, forming the essence of the elements. After this task was done, she removed herself from activity, imbued herself in all mundane, and went into a permanent rest.
She is never seen, but is omnipresent on the mundane spheres. Her main daughter, Adyani, could be an avatar or aspect of her, perhaps. Adyani and her daughters refer to Æna as "siress" and "Grandmother" and Womb of us all.
Oxo was known as the black wave, the formless dark, the black amoeba. This entity was the first spirit to shun the light, seek the dark, and tapped the Anti-power at the end of the Ocean. The creature, lacking mental energy but aware with alien supra-cunning, gained extra power from consumption. Forming the Deep Old, it sent corruption and destruction. It brought consumption to the once-utopian life cycle, bringing carnivores, rot, decay, and the like to what was once an everlasting life cycle. Oxo according to legend was responsible for the rise of reptiles and dinosaurs on Ærth.
Oxo was finally checked by the High Ones. These being began a long war with him. Alhuhax, lord of the High Ones, finally slew his form and scattered his subordinates. Oxo is "dead" but as one of the Eld, who can say whether or not such a creature can be destroyed. Perhaps Oxo is imbued in all Evil now-or maybe he awaits or regenerates in a realm beyond Immortal's knowledge. Who can say?
This Trinity is described just to provide an overview of the pantheon. These entities aren't worshiped, but they are important to the overall whole. They also give the gods something to fear.
The Deep Old are the offspring of Oxo. Oxo birthed several powerful gods from his consumption and negative heka.
The Deep Old are demonic, chaotic, monstrous gods that tend to represent animalistic and evil nature. They gained strength in the mundane spheres long ago because of their affinity or with reptilian and insectian natures, as well as monsters and serpents and demons and other dark entities of nether origins. They also lord over chaos and demonic races too. All seek domination and their own mysterious ends, though they see humans as best as chattel to be exploited.
The Deep Old were exiled when Oxo was killed by Alhuhax, and have been forced behind the scenes by the tarpings of civilization and the work of the High Ones. They were also subordinated when one of their member, Demogorgon, decided to exploit humanity and thus gained power and status, using order to serve his dark ends. Yet, they have not lost their power in the "Outer Dark", and any foothold they gain on the Mundane planes could tip the balance.
Known Deep Old
The Deep Old should be considered similar to those Deities found in the ficticious work of Mike Moorcock or H.P. Lovecraft. They are meant to provide the level of chaos and fear that can't be gained from the Dark Maquis.
The High Ones were initially the spiritual entities and deities created by Æna. Adyani, her "daughter", had several daughters of her own, who handled the affairs of nature. Technically, this race would count as being "Ancient Masters" as well, but they joined the second wave.
During the time of great darkness, when Oxo and his deep old were threatening the utopia that Æna created on the mundane and in the Æther, including early humanity, EA appeared and sent a bolt towards the bright realms. From that the High Ones were awakened, a humanoid race of gods, and from this place built a city in the Supernal Spheres. Whether EA "created" them is a subject of debate, but it is more likely he summoned a race of entities that formed on the Supernal Spheres. This race of humanoids, lead by Alhuhax, fought the influences of the Darkness, slew Oxo after a lenghty battle, and shattered the Deep Old's hold on the mundane.
During the battle, to keep the mundane balanced and to lessen the power of the Deep Old, one of the High Ones, Honryu, took much of the power of Negative Heka, that dealing with Death and Darkness. Honryu took over the Twilight Realms, and his nature ended up forming a "shadow guild", an "underground" in the city similar to what is formed today in human cities with crime guilds. This split enabled the coming of Demogorgon, who exploited this weakness and gave the High Ones a new enemy to fight.
Known High Ones (Not listed still forming them )
JMs creating this race should think of the "Classic" pantheons of Western Civilization when forming or fleshing out this pantheon, as well as those from most modern fantasy literature and RPGs.
One of the Deep Old was an entity called Demogorgon. When Oxo was slain, this creature retreated to dark realms. He looked at the race of the High Ones and the Race of Humanity and saw weaknesses weaknesses he could exploit.
With the races he controlled, and created, he gained power. He stole some races from Honryu's Twilight Kingdom, such as the Devils. All these races serve him as his Dark Marquis. (While Demogorgon's subordinates are Kings or Princes in their own rights, he forces them to refer to themselves as Marquis as a symbol of respect and fealty.)
Known Dark Marquis
JMs should treat The Dark Marquis as a sub-pantheon of demons. Inspiration of this comes from the various Fantasy RPGs out there that deal with such entities, including AD&D. Much inspiration of this comes from the way EGG structured his Gord The Rogue Books, with subraces of evil serving Infestrix, Graz'zt or other races.