The Great Ones
Providence: Overseer of Nature, Mouth Piece of the World
There are many Great Ones that live upon the surface of Avernus, but none is so influential and yet as well hidden as the one known as Providence.
Considered the weakest of the Great Ones, Providence is charged with overseeing the multitude of biomes and the species within them, that exist upon the surface of Avernus. Its duty is not to perform experiments, or to assist in their development, it is merely to observe and correct issues that arise before they become issues.
A drought in one region which could cause ecological collapse, a lack of food and minerals in another. These things Providence sees, sometimes thousands of years before they become issues and corrects them ensuring that the works of its eternal director are carried out without any delay or distraction.
Providence also serves as the occasional mouth piece of the World when it requires one. This has rarely happened, but when it is needed, for example the ascension of a People to Guardian, it serves as its conduit.
While the weakest of the Great Ones Providence is still a Great One, an Apex psyker of such potency that all the Peoples of Avernus would need to band together to defeat it. Its specialised powers lie within mass scale geomancy and matter generation, able to create material for entire worlds and shape it however it pleases.
Yharon: The Most Honoured, the Flame of Hell
The only Great One to have not been directly created by the Planet Mind Yharon began its existence as a precursor species to what would eventually become the Therondy Dragon millions of years ago. Most of the details of its history have been lost, but what is known is that it gave its life to defend Avernus from some foe in this distant past, though what has been lost.
Regardless for this service Yharon was taken by the Planet Mind and personally reworked into a Great One, a massive being of fire and death, whose words can shake entire suns to nothing.
Yharon was also used as the basis for a new generation of its kind, the modern Therondy Dragon, significantly more powerful and intelligent than previous generations possessing pale imitations of their progenitor's abilities.
Its unique ability is over language. Its status as the originator of the Dragon Tongue and most Avernite pantheons which include the Great Ones worship it as a bringer of language. As such Yharon is capable of taking language away from his enemies, removing their ability to structure their minds around it, reducing even the mightiest to mere beasts.
The Wheel of Fortune: The Ever-Seeing Eye, Panopticon.
Avernus is a most busy entity, but in turn it must keep abreast of developments in the greater chaos of the galaxy, if nothing else to ensure that watchful eyes do not fall upon it.
The Wheel of Fortune is the Great One assigned to observe the galaxy, watching, cataloguing and considering information and data. There are few major events that it does not see and none pertaining to Avernus are not seen for that is its special power.
When something occurs that may affect Avernus the Wheel of Fortune will react in response. If the event is minor, or beneficial it will do nothing, if it is detrimental, but not too potent, it will use its vast fate weaving abilities to ensure that it will never come to pass.
If the threat is too vast for that, then it will prepare Avernus for its arrival.
The Wheel's special power is fate weaving, at which it is possibly the most practised user in the galaxy. Combined with its divinatory prowess and vast power it is an extremely dangerous foe.
Calamity: Vengeance, The Balanced Blade
An unusual Great One, Calamity is intended as retribution against those who attack Avernus, although it has never been used in that capacity.
As such Calamity spends most of its existence sleeping rather than performing a specific task for Avernus and has only been awakened to defend it against Daemonic Incursions.
Calamity is one of the Stronger Great Ones in terms of psycic strength, but it has one of the most potent unique powers of all, control over the concept of misfortune. The most obvious usage of this power would be that any being that attempts to strike Calamity will find itself plagued by misfortune and bad luck, while Calamity will have nothing, but excellent luck, giving it an enormous advantage.
However, what would make it so potent as a weapon of retribution is that Calamity can apply this ability to entire empires, cursing a stellar civilisation with naught, but misery, while sending all their good luck to their enemies, dooming whatever was foolish enough to attack Avernus to an ignoble end.
The Golem: Eternal Warden
Not a living being with a traditional Soul, the Golem is instead an artificial construct given a soul by the Planet Mind, one of the two to be created in so unique a manner. A vast stone construct the Golem is charged with protecting many of the most sensitive locations the Planet Mind knows of, including its access point to its Maker's webway, the Abyssal Depths and the Hidden Plain.
The Golem distinguishes itself from the other Great Ones in a very simple way. It is the physically strongest and most resistant of them. While the Serpent maybe more powerful, the Radiance, capable of affecting more beings at once and Lady Death the most skilled, the Golem can obliterate entire worlds with its strikes and its hide can weather almost any attack, psycic or material.
Its other ability is that it can operate multiple bodies at the same time, in order to protect its various charges. If its full might were ever focused upon a single enemy, then it would have to be a strong foe indeed.
The Only One: People's Champion
The other in organic Great One, Only One is an inanimate object. What it is in its base form is unclear, as it takes the form best suited to it, but when take up by anything capable of withstanding its power the white crystal existence reveals itself.
It is possible it was meant to create an existence equal to the Black Crystal Sword of its Makers, but it did not succeed. However, something different was created instead.
One of the most storied of Avernus's Great Ones Only One has moved from host to host longer than any can remember, testing the best of the People in accordance to a mysterious design, dictated to it long ago by the Planet Mind.
When a host capable of withstanding its power picks up the blade it connects with them, the barest fraction of its overwhelming psycic power running through them, turning them into a warrior without peer.
However, Only One's capabilities are a mystery even to itself to an extent as it has never been utilised to its maximum potential, as no host can handle the full unbridled power of an Apex Psyker, with the higher of the People's muttering that the Ancient Wonderer maybe the single being who could, although this is speculation, influenced by her legendary reputation.
What is known of its powers is that it acts as an immense psycic amplifier, turning even the weakest psyker, or even a non psyker, into an incredibly powerful being. This is in addition to the memories and skill of all it's past wielders being accessible to the user making them an impossibly skilled foe.
In the current era, Only One's host is unknown, if it even possesses one at this time.
The Shattered Lord: Celestial Monarch
Very little is known of the Shattered Lord, only that at some point in its history it was broken apart, although the reason why varies. Some say that it betrayed or harmed the World, other that it was the only way to save it.
Which ever it was, this Great One is mostly spoken of in legends alone, telling of an enormous being of star flesh that defended the World in its earliest days.
The legends also say that it was broken into several separate parts.
Its brain, three eyes, spine, heart, lungs, torso and spirit.
If all 10 pieces were to be recombined then the Great One would be reborn, but only the Planet Mind knows the location of these fragments.
@Durin
Just ideas for Great Ones.