The Circle of the True

The natural world exists in a fragile equilibrium. Elemental forces like volcanic fires and raging tempests are balanced against living plants and animals and the fey spirits of the land. Predator balances prey. Planting balances harvest. Wilderness balances civilization. The cycle is self-sustaining, and the druids stand as the protectors of this cycle. Which is why aberrations are so loathed among them. These alien creatures of madness and dreams are fundamentally unnatural, even more distantly removed from the natural world than fiends and celestials. Their very presence corrupts the world, warping and twisting living things to reflect the horrific home of the aberrations - the Far Realm.
The Circle of the True is a loose collection of druids who have chosen to stand, first and foremost, against aberrations. They study their prey as a naturalist dissects a beast, dispassionately and pitilessly. They seek to understand the nature of various aberrations, to better fight against them. They call upon elemental forces that aberrations find toxic - a deep expression of the fact that their world and ours are incompatible. They seek out gates to close them. They seek out cults to quell them. They seek out villages to prepare them.

Legend of the Living Gate

The Circle of the True keeps an oral history of their organization through the millennia, and they trace their origins into the primordial past, when divine wars shook the young world and impossible, apocalyptic beings battled while mortal life cowered in the tall grass below. It is said that in this ancient time, powerful wizards began to explore the multiverse beyond the world. According to The Circle of the True, this was a culture they call the Elder Elves. Other traditions identify long­forgotten empires or arrogant deities. The exact identity doesn't matter so much these days - what matters is these wizards pushed so far beyond the world that they made contact with something that was older and vaster than the world by far, something of strange geometry and alien thought, something that broke minds and corrupted bodies. What the wizards contacted was dubbed the Far Realm. This broke the multiverse.
What followed in the wake of that first contact was nothing less than an invasion. Mortal races were exterminated en masse, magic was broken, and chaos reigned. The warring gods paused in their battle to attempt to repair the world, to sever its ties to the Far Realm and to protect what they had begun to create. They created a vast crystal lattice of solid thought and reason, a ward to keep the Far Realm at bay, and called it the Living Gate.
The Circle of the True traces its origins to the construction of the Living Gate, as a group of mortals endowed with the responsibility to protect it and preserve it. Some say the gods themselves gave this duty to the ancient group that became the Circle of the True. The name of the organization comes from this foundation - that they must be True to their oaths, to protect the world from what is beyond the Living Gate. To defend the world required people deeply in touch with the world, and the Circle of the True were that.
They failed. It was not long, on a cosmic scale, before the Living Gate was shattered. Stories differ as to who or what broke it - a rogue deity, a powerful archoelemental, a great cosmic entity from the other side, a single curious human. The point is that it shattered like cheap glass and its fragments were flung to the far corners of the multiverse. The Far Realm was unleashed, and remains so to this day.

Slayers and Seekers

Today, the Circle of the True seeks to protect the world as best they can, given the flawed state of the multiverse. They play host to two major factions.
The first major faction of the Circle of the True is the abolishers, druids who have become aberration-slayers. Abolishers find enclaves of creatures from the Far Realm, and use the elemental blessings of the Circle of the True to snuff them out. To be an abolisher is to be an elite member of the Circle of the True, one of its battle-scarred champions and one of its powerful leaders.
The second major faction of the Circle of the True is the guardians of the Living Gate. These druids feel the weight of their ancestors' failure, and seek out fragments of the Living Gate in the hopes of someday repairing it. They scour the multiverse to find even sand­ grain-sized pieces of the great structure, and use old spells to protect the world as they do so.