The Silver Flame is a gestalt celestial force that was forged in the Age of Demons, when the couatl sacrificed themselves to bind the overlords. Its power has been wielded by many champions across the ages, across the world. The Silver Flame is not a god. It was created for an explicit purpose: to be the cage that keeps the apocalypse at bay. It cannot influence the world on its own but can empower mortals to fight for it. Ultimately, it is a resource to be used to fight against evil. The Silver Flame protects the entire world from the overlords. It doesn't elevate any culture or ancestry, and by extension, those who wield its power should protect everyone from evil.
Cool, but what is it?
It could be that the Silver Flame is exactly what it seems to be, a gestalt celestial entity formed from the collective immortal essence of most of Eberron’s couatl. It is a force that permeates the world, like gravity, and while there are locations where expressions of it are visible, it’s not a thing you can really see or visit.
The exact nature of the Silver Flame isn’t known, but there are likely multiple theories debated by scholars. One such theory is that the Flame is a vast, continuous metaconcert maintained by the couatl. The argument for this theory is that the couatl were psionic, and often blurred the line between the psionic and the divine. The existence of the shared dream of the Masvirik’uala seems to support this theory: as far as anyone knows, they don’t go to Dal Quor when they dream, so are likely “dreaming” within the Flame.
It is also possible that the Silver Flame blankets the Material Plane in a manner like the Border Ethereal and could be considered its own (artificial) plane of existence. This theory also allows for the Masvirik’uala to dream within the Flame. Planar-powered magical phenomena are not unheard of on Eberron. Irian and Mabar are examples, with energy from both planes powering Aereni deathless and undead respectively. This theory also allows for the possibility of travelling or seeing into the Flame itself.
Couatl and the Silver Flame
The Unknown are celestials native to Eberron, mythologically the last children of Siberys, and much like the children of Khyber, the couatl were born in the first age of the world. They appear as magnificent, feathered serpents, often depicted by the Church of the Silver Flame with rainbow-coloured feathers, though whether this is how they all looked or is an artistic representation of the specific couatl that came to Tira Miron in her vision is uncertain.
The couatl originated on Sarlona and are believed to have formed from the blood of Siberys after he was killed by Khyber. The couatl were content to remain in Sarlona and let the dragons and other mortals explore the world until the rise of the overlords. When the fiends rose, the couatl initially fled to the continent of Xen’drik and hid, until they were eventually found by the dragons.
Together, the couatl and the dragons went to war with the overlords. Two of their greatest sages, Hezcalipa and Ourelonastrix, discovered the Draconic Prophecy and the way to manipulate the future. The balance of power during the first age favoured the fiends. The couatl soon realised that there was no scenario where the overlords were defeated without the couatl’s sacrifice.
Led by Hezcalipa, the couatl abandoned their bodies and fused their immortal essence together, creating a well of pure divine energy, the Silver Flame. The Silver Flame could bind the overlords as they were defeated by the dragons and other mortal species. Various groups that worship the Flame believe that it is strengthened and reinforced by mortal souls.
While they were not completely removed from the world, the couatl are thought to be extinct as individuals. In their final days, the couatl prepared human volunteers from Sarlona, and tasked these humans with guarding their ruins, eventually creating the shulassakar and thus yuan-ti. The couatl also created the shared dream of the lizardfolk that would become the Masvirik’uala, or Cold Sun Federation. The lizardfolk guided by these dreams work to prevent the release of Masvirik, the Cold Sun.
Aasimar
The Silver Flame is one of the most common sources of aasimar on Eberron, creating more of them than any other force. The shulassakar are effectively one form of Silver Flame aasimar, but not the only form this blessing takes.
Silver Flame aasimar appear like their parent race, so human aasimar appear to be human, lizardfolk aasimar appear to be lizardfolk, and orc aasimar appear to be orcs. Many of them may also manifest some of the traits of the couatl, making them appear more like the shulassakar, such as serpentine eyes or rainbow-colored hair.
Silver Flame aasimar are guided by the Flame, though the form that this guidance takes can differ depending on the aasimar’s culture. For aasimar in Thrane, who follow the Church of the Silver Flame, this guidance is delivered by Tira Miron, the Voice of the Flame. As an extension of this, individuals that become the Keeper of the Flame also become aasimar of the Silver Flame.
Silver Flame aasimar also appear among the Ghaash’kala and the Masvirik’uala. The Ghaash’kala are guided by Kalok Shash itself, which appears to them as a group of spectral beings, some of which they may recognize as other Ghaash’kala who fell in the line of duty. The Masvirik’uala are guided by their shared dream, the messages and stories depicted within pushing them in the right direction.
All these cultures respect the aasimar and seek to put them to use. The Silver Flame doesn’t choose people for no reason. An aasimar surely has a greater calling. Any aasimar of the Silver Flame may also receive guidance in the form of a couatl appearing in dreams or visions. It could be that Tira Miron was an aasimar of the Silver Flame herself.