Umbral Bond

Umbral Bond is an assembly of remnants. Remnants of old forgotten and now broken religions from times that were much darker, and gave birth to much darker theologies. And a lot of things that simply no one know what they actually are, and how they came to be. Their influence on the world was in most of cases older than the Grand Empire itself, but during the Second Era they were mostly quarantined successfully.
When the Twilight War occured, many things changed. The monstrosities of the long gone times have began to stir in their slumber. Not only have they breached their containments (at least in case of those that were at least somewhat contained). To everyone's absolute surprise, they began to either cooperate, or at least ignore each other's forces instead of fighting against each other on any occasion. Such was the genesis of the modern Umbral Bond.
Their goals are as enigmatic as the entities themselves. Is this a form of self-defense against encroachment of more modern eldritch abominations of the Pentagram? Or perhaps the collapse of the empire and the everpresent chaos has awakened the ambitions of those forgotten deities? Not all of them has awoken to the same degree, and some appear to be pursuing entirely different goals. So perhaps more of a mutual assistance treaty? In the end, nobody knows.
What all of the 'deities' of the Bond have in common is that they are capable of intentional deformation of mortals and other forms of live, altering their bodies and minds in a way that goes much deeper than genetics or brainwashing. Some appear to also have supernatural servants, but majority depend on the mortals to achieve their enigmatic goals. They all, however, depend on their corruption and brainwashing to create their sects, as very few of them can offer anything that sane mortals might consider to be acceptable or useful.

Structure

Introduction

The heads of the Umbral Bond are the Ancients, a handful of incredibly powerful eldritch abominations that has managed to (somehow) communicate with each other enough to establish an alliance that created the faction. Each of them is completely different entity with different magic, different forms of corruption, and different goals. Naturally, each of them is practically a different branch of the Bond in itself, with numerous mortal sects and more... exotic servants toiling underneath them.
The imperial scholars keep track of approximately thirty-five Ancients. Some are however mostly inactive, and their addition to the list is based on the logic that if it's ancient and damages sanity, it has almost certainly joined the Umbral Bond - in two cases when such Ancient resumed activity, this logic turned to be correct. While those Ancients remained inactive for centuries, once they 'reawakened', their followers did, in fact, cooperate with other members of the Bond.
Some of the Ancients are more active, some are less. Some are a nuisance, others conquered vast swathes of territory in the past and now hold sway over minds of millions. None, however, should be underestimated, regardless of how irrelevant they appear. Their intellects are to mortal ones as they are to ants, and while often have problems noticing the finer details of something so minor to them, they can be frighteningly devious.

List of Notable Ancients

Ancient of Blood is an ancient overlord of the Telyan continent, who created the first beastkin by merging humans and animals in order to create his perfect servants. Bloodthirsty beasts, yet intelligent enough to organize twisted rituals during which whoever they capture (be it other beastkin, or captives from their raids against anyone else) is killed by being slowly drained of blood that is then offered to the Ancient. Nobody knows how many millions of people were killed that way during the many millenia. However, while the Ancient of Blood is strong, his domain is under constant assault from the forces of the khardic Overtyrant (himself a benevolent deity... with truly Ancient-like aesthetics) and is slowly shrinking.
Ancient of Depths is an enigmatic figure behind the tragedy of the ancient dragon Azirkhavir and his petty empire on one of the many isles of the Inner Sea. He offered to allow Azirkhavir to have healthy children, freeing him from the ancient corruption permeating his blood - in exchange for sacrifices, that were to be thrown down one of the many pitch-black shafts in the ruins of unknown civilization on the island. When the demands for sacrifices grew too large, Azirkhavir attempted to launch numerous wars of conquests to satisfy the mysterious entity's demands. Following his defeat in the Flame Wars, he attempted to weasel his way out of the deal, only for his entire empire to be snuffed out in a single night. Leaving only a set of isles that almost no one returns from.
Ancient of Filth is an Ancient that has mostly evaporated during the Twilight War, with some madder scholars suggesting that (s)he ascended into high godhood, resulting in the birth of the Rampant Bloom. Cults dedicated to him still persist, and new ones are born. There might still be some life left in this ancient abomination of rotten roots, parasites and toxic sludge, who in his prime has corrupted numerous Fae into insanity. Or perhaps it's dead, but exist on the level where it simply no longer matters?
Ancient of Frost, also known under the name of Nythrathril and under monikers of Frost Father and the Doom of Lomar. He is the entity responsible for the destruction of Lomar (the first human kingdom in Karadia), and has only grew in strength since then. Today, through thousands of thoroughly corrupted ice elven priestesses (each one being his descendant - and a lover, if some tales are to be interpreted literally), he is de facto ruling the Ice Kingdoms, Each year tens of thousands of warriors take up swords and invade the Grand Empire, Visenian Commonwealth, and the Kingdom of Niflheim, with his name on their lips.
Ancient of Nightmares, whose true name remains unknown. He was unearthed in the Needle Mountains during the Twilight War, when the desperate antegnite mining operation descended a bit too deep and ruptured something that shouldn't be ruptured. Today the Reality itself breaks apart near the breach, and anywhere within ten kilometers from that place the borders between what is and what isn't are blurred. Within the mines you can be murdered by your own hallucination, and those whose minds and forms are too weak will find themselves being turned into illusions, and promptly snuffed out. The lack of conscious actions from the Ancient of Nightmares led some scholars to theorize that he was merely disturbed in his slumber, and is projecting such an effect despite still being de facto asleep. If that's true, then nobody is willing to see what happens when he is truly awoken.

Military

The actual power of the Umbral Bond greatly varies between the Ancients in question. Some, like the Ancient of Blood or the Ancient of Frost, have millions of mortal servants. Others, like Ancient of Depths or the Ancient of Nightmares, have very few, but instead possess more supernatural servitors, each of them a class in their own. Some of the weaker (or, perhaps, more elusive in nature), like the Ancient of White or Ancient of Horror, appear to be 'almost' harmless, occasionally spawning a cult or two, acting through various books and artifacts, and generally having a minuscule presence in Reality.