'The Titan Locus is a fanon creation that has no link to canon lore, feel free to use or disregard as you see fit'
The Titan Locus is an artifact of great power that was placed on Azeroth shortly after the defeat of the Black Empire. The device was created by the Titan, Khaz'goroth and blessed with a portion of each of the titans who had raised up the titan-forged and their leaders, the Keepers of Azeroth. The purpose of the locus was to serve as a backup device. Should the old gods return and corrupt or worse, kill any of the titan keepers, the Locus could be used to elevate a replacement chosen by the remaining keepers. The replacement would have all the power and immortal status of one of the original keepers, and would be able to fulfill the duties of the fallen keeper to ensure that Azeroth remained free from the corruption that was the Black Empire.
Because of the power that was contained within the Locus, knowledge of it was kept secret, even from the keepers themselves save one, Archeadas, the keeper elevated by Khaz'goroth himself. All the other keepers, including Highfather Ra and Prime Designate Odyn were left in the dark of the devices creation, purpose and location. In order to ensure that it was never found by any of the titan keepers before it was necessary for it to be used, a vault was constructed in secret by Archeadas and once constructed, was placed under the guard of one of Archaedas most powerful servants, the earthen smith, Astus Forgewright. The vault was then sealed, and all records of its existence scrubbed from the titan databases, to ensure that it remained hidden.
Sadly, the hidden status of the Locus meant that when the time did come for it to be used, it was far too late. When Yogg-Saron corrupted Loken, the events that followed meant that Archeadas never had time to return to the vault to secure the Locus, nor did he want to risk it falling into the hands of Loken, as he feared what might happen he were to hand over such a power to the old gods. He kept it hidden and secured himself away in Uldaman even after Tyr sacrificed himself. When it was safe he would awaken and reclaim the Locus, then he would set about using it to replace the fallen keepers, depending on how many survived.
The locus however would not remain hidden forever. Eventually the vault that hid the device was discovered by one of the Vrykul, a shieldmaiden named Aellaskal. She summoned her companions, many of them notable leaders of the settlements that had been constructed on the islands surrounding the vault. Upon entering the vault, they unknowingly woke the guardian Astus Forgewright, who when told about the state of the world above, attempted to initiate primary protocols which ordered him to reach out to the keepers. Sadly he was unable to do so, as the devices that allowed for communication with the outside world had been damaged over the years and were completely unusable. Seeing no alternative, Astus engaged his secondary protocols, which ordered him to use the Locus to create new keepers, beings who would be able to use their considerable power to protect the world from the might of the old gods. He offered the locus to the nineteen who had accompanied Aellaskal and they all tasted the power that had been placed within the Locus. Each of the nineteen were elevated to positions of godhood, yet none of them had the full power of a keeper, as the power had been spread among far too many individuals.
Once the Locus had been used, Astus and the new gods and goddesses of Imbringen decided that it would be best if the Locus were buried forever, as they could not risk another finding the device, as Aellaskal had. The vault was sealed and the tunnels leading to it collapsed permanently, ensuring that the Locus would be buried forever. Only the might of Archeadas would uncover the vault from that moment on and sadly for Archeadas, the titan keeper never got the opportunity as he was slain by adventurers who sought riches in the depths of Uldaman, and all his secrets, including the location of the Locus, were lost with him.