Foregone Fables - The Story of Tartarus

Like any good series, RWBY has a lot of things going on behind the scenes. There are feint, subtle hints given that there are things going on far beyond Salem and Ozpin, far beyond the Gods and Relics. Our current story is no different from the ones about Roman and Cinder in volume 1-3, and Foregone Fables emphasizes that.

Tartarus is a perfect example. Who is Tartarus? It is not mentioned in either timeline, and likely never will, but its part in the story is greater than you think. Tartarus is the Dragon that dwelt under Mountain Glenn and destroyed Beacon Tower in volume 3 of RWBY, or the Dimmed Beacon Saga in Foregone Fables. And no, that isn't its "official" name. We just figured out that this important character needs to be called something in the AU.

This Dragon, unlike a popular belief, is not related to Salem. It was independent of her, predating both her and the Parasite who had possessed Ozpin in her time. Tartarus was a Dragon, one of the most powerful species of Transdimensionals; The mass of its bio-energy was so great, that it would continuously shave off its substance and generate pools from which smaller beings can form.

This Dragon flew across Remnant four thousand years ago, terrorizing human societies, and was at least partially responsible for the destruction of several kingdoms. However, once in the northern wasteland of the continent that will later be called Solitas, Tartarus attacked a small bandit tribe and invoked its leader, the Mystery Maiden Longinus, to attack it and its children at full power. Though Longinus didn't survive the output, Tartarus' horde was decimated and the Dragon was gravely injured. It flew to the other side of the planet and created a mountain around itself, resting underneath it in order to one day recover from its wounds.

The deeper layers of the mountain Tartarus created contained black crystals inside which Tartarus stored the damaged parts of its body before re-absorbing them as they stabilized. Even in its slumber, Tartarus' body kept on producing bio-energy; Its great amount of psionic power has allowed it to communicate and control the excess of the beings created from it even when hibernating. In the thousands of years that passed, its existence was forgotten and the mountain Tartarus created became known as Mountain Glenn.

Tartarus' slumber was interrupted for the first time when the kingdom of Vale has settled in that mountain, and its creatures rose up to explore. The multiplication of Grimm in the area caused an interest in the eyes of Merlot Industries, a research corporation owned by the Schnee Dust Company, whose workers and researchers would steal and experiment on Tartarus' children. Although not awakening the beast, Tartarus' rage caused its creatures to storm at the city and destroy it. Ironically, the citizens found sanctuary underground, closer to the Dragon which led to their death.
Tartarus was interrupted a second time when the White Fang, guided by Roman Torchwick and Cinder Fall, had made their own bases underneath the mountain. Knowing of the "tragedy", a scheme was made to use powerful bombs made from Dust that Torchwick stole to dig the Grimm in the caverns a way unto Vale. Tartarus' children did not react with much force, and the operation was successful, only for the attack to be repelled and the tunnel resealed. After that, huntresses from Beacon went to check the caverns to find remains of the work of Merlot Industries and narrowly escape a leftover White Fang bomb, and left as quickly as they came.

Tartarus' slumber was finally broken months later, during the fall of Beacon. Its mastermind, Cinder Fall, had very little knowledge of Tartarus and its children, and had deliberately caused mass panic in Vale to lure them out. This way Tartarus' creatures sensed the fear and ran after it; The accumulating fear became great enough to awaken Tartarus itself, and the Dragon joined Salem's creatures and its own in the attack.
In the canon timeline, Tartarus flew above the city and into Beacon Tower itself, destroying it, and prepared to attack Cinder, who it knew was the one who awakened it, however, the Dragon was incapacitated along with her when Ruby Rose unleashed the fullest of her Medusa power on them. It could not destroy Tartarus completely, but it could seal it in stone, leaving its children to loom under it, mourn and try to revive their master and progenitor for years to come.

In Foregone Fables, Tartarus was not petrified, but Cinder prevented it from devouring her by stunning it with a fireball before leaving, and the Dragon realized Cinder was far too powerful for even it to destroy. Moments later, the once-human who put him to sleep millennia ago had found its presence and now far stronger than before, she put an end to Tartarus' life. However it could not be placed to rest, as the Godslayer has stole a part of him. The Dragon's brain was used by the one who resurrected her to create a line of mutant Dragons, first seen during the fall of Haven.