Corpus 002 was a Great Existence responsible for the descent of BR-002. The circumstances of how it came to be within the Hypercube mine W-31 where the Black Ring appeared in N.F. 104 is unknown, but the Corpus fed off the panic, anger and desire to survive of the Rustfire members who were massacred by Nirvana automated mining robots. Three days later, it was defeated by the Underground Shepherd, and although its Corpseborne body was cut in half, the Corpus avoided being devoured by the Shepherd. The Corpseborne's upper half survived for the next decade, on the brink of life and death, and spent years slowly spreading Mania and devouring humans' spiritual energy in secret. The lower half of the Corpseborne was buried deep at the bottom of the Black Ring. Somehow, the energy consumed by the living half continued to be transferred to the dead half and leaked as contamination into its surroundings.
In N.F. 113, it regained the power to create a new Black Ring by fusing with Julien at the end of the Ten Days of Rustfire. It became master of the strongest Black Ring ever recorded outside DisSea and briefly expanded its domain to cover all of Syndicate before it was defeated again, this time by the Chief, who turned the collective will of the people of Syndicate against it, stripping it of its power and destroying its Ring for once and for all. Despite this, the Corpus survived a brief time longer before it was finally found again and consumed by the Underground Shepherd.
Corpus 002 possesses the most insidious powers of any known Great Existence, able to conceal its presence and contamination from Mania-detection systems, and whisper into people's minds to influence them with fear. Like all Great Existences, its behavior is strongly shaped by the influence of the human minds from which it took its form, in this case, the fighters of Rustfire. Corpus 002 is obsessed with revenge and survival at all costs, and quickly becomes arrogant when in a position of power over its enemies.
Role
Drifter Camp
After almost a decade of hiding, Corpus 002 reappeared in N.F. 113 and its presence was detected at the site of BR-004. From there it traveled across Syndicate to Drifter Camp, drawn by the similarity of the camp's residents to those who had given birth to BR-002. There it covertly enveloped the Camp in a mental contamination field that could directly capture individuals' consciousness and consume their spirit from within without leaking any contamination that would trigger a Mania-monitoring system. Its upper half was defeated by the Chief and Oak Casket, but not before it was able to restore enough energy to bring its lower half back to life. As panic spread through Drifter Camp and a new Black Ring threatened to form, the Chief succeeded at provoking the Corpus into open battle. They narrowly defeated it, but the Chief was prevented from consuming it by the activation of the Rules within their body.
Oblivion Depth
Over the next three days, the Corpseborne escaped and continued to feed. The Chief eventually tracked it to a secret prison run by the Reconstruction Executive Committee, where they battled again. Through the connection between its halves, the Chief and Hecate destroyed its lower body, severing the link; at the same time, the Chief marked its upper body with the Shackles. They intended to make it impossible for the upper body to hide itself again, but they suffered severe backlash again from the Rules, as well as from the Mania energy of the Corpus itself, and fell into a deep coma. As the Ten Days of Rustfire broke out, the forces hunting it were distracted by new crises and the Corpus was left to its own devices, able to rampage freely and grow in power as Syndicate descended into greater chaos than ever. Eventually, recognizing in Julien the same emotions as the people who it was born from, the Corpus fused with him to create the largest Black Ring ever seen in Syndicate.
Towering Black
Julien and the Corpus struggled for mental control of the Ring for several months, but thanks to the work of Parma, the Corpus ultimately came out on top. BR-002 rapidly expanded over all of Syndicate; feeding on the entire district at once, the Corpus finally believed itself powerful enough to be undefeatable by anybody. As the Underground Shepherd entered the Ring, the Corpus diverted all its attention to stopping her, which allowed the Chief to go under the radar and reach its main body at the top of the high tower.
The Corpus expressed that it had almost forgotten about the Chief's existence, believing itself to be that far above caring about them, but was shocked to discover that the Schorl accompanying them is capable of harming it with the Rules. With the Rules restraining it, the Chief stripped the Corpus of its strength by empowering the people of Syndicate who were providing the energy that fueled the Black Ring. The Chief correctly surmised that the people remaining in Syndicate were not the violent chaos-lovers (who had been annihilated and subsumed into the Ring's first appearance during the Ten Days of Rustfire) or the weak and fearful (who had fled the District since the beginning of the crisis), but rather the survivors who were determined to persist throughout everything. These survivors turned their will to live and to see a better future against the Corpus, shredding its protections and dissolving the Black Ring entirely.
Despite its Ring being destroyed, the Corpus managed to avoid being consumed by the Chief and thus, though shattered and severely weakened, managed to survive by attaching itself to the spirit of Rustfire. It fled, intending to once again lie low and regain its power, but unexpectedly found itself drawn — compelled against its will by Rustfire's desire for revenge — to the DisSea that it had been avoiding. There, it was found by the Underground Shepherd, who finally consumed it and ended its existence.