Vigil: the Prothean watcher of Ilos

Vigil was a Prothean virtual intelligence installed beneath the surface of Ilos, an advanced non-organic analysis system carrying the personality imprints of Ksad Ishan, the Chief Overseer of the research facility it was built to watch. Left alone when the Reapers swept the galaxy fifty thousand years before, it kept a handful of sleeping scientists alive long enough for them to reach the Citadel through the Conduit and sabotage the signal that governed the keepers. When Commander Shepard came down into the archives in 2183 on the trail of Saren Arterius, Vigil was the only surviving witness able to explain what Sovereign had come to do. (Mass Effect)

A mind copied into a machine#

Vigil was not an artificial intelligence in the sense that galactic law feared. It was an analysis system of considerable sophistication, built to hold and act on the priorities of a single Prothean, and the personality it presented to visitors was assembled from imprints of Ksad Ishan, the chief researcher who oversaw the Ilos complex. What survived of him in the machine was authority, patience, and an absolute commitment to the project's purpose, which was to break a cycle that had already been running for millions of years. (Mass Effect)

By 2183 the interface had suffered badly. Its hologram flickered and broke apart as it spoke, the shape of a Prothean worn down to something barely legible, though the memory core beneath it remained sound. It had been listening to the communications of the intruders moving through the ruins above, and it used that traffic to translate its own output, so that a human, an asari or a turian standing in the Watcher's Chamber heard it plainly rather than in a dead language. (Mass Effect)

The world the Reapers overlooked#

Ilos had been a jewel in the golden age of the Protheans, a green world crowded with spires and arches. Older still: the inusannon had lived there before the Protheans discovered the planet and settled it themselves, a fact the surviving Prothean soldier Javik would later confirm. By the time anyone returned, the surface had been changed to the colour of rust, oxygen levels had risen, and lightning-set wildfires burned across the night side with no respirating animal life left to flee them. (Mass Effect; Mass Effect 3: From Ashes)

The facility below survived by accident of paperwork. Records of the Ilos project were destroyed in the initial wave of the harvest, so the Reapers came and went without ever learning that a research station existed there at all. The staff sealed themselves into an underground complex, entered cryogenic suspension, and left Vigil to keep watch until the galaxy was quiet enough for them to wake and begin again. (Mass Effect)

The contingency#

The plan assumed the Reapers would finish quickly. They did not. Grinding the Prothean empire down took centuries, and across those centuries the complex bled power it had no way to replace. Vigil responded exactly as it had been designed to. It deactivated the cryogenic pods one at a time, killing the sleepers inside, so that what remained in the reserves could be concentrated on the pods that mattered most. (Mass Effect)

Almost everyone in the facility died that way. When the Reapers at last withdrew, twelve top scientists were brought out of suspension, and no more. Twelve were not enough to rebuild a species. Confronted about what it had done, Vigil did not plead necessity or malfunction. It stated that the eventuality had not been entirely unforeseen and that it had followed contingency planning laid down in advance, which left open the uncomfortable question of whether the non-essential staff who died in their pods had ever been told what the contingency contained. (Mass Effect)

The twelve and the Conduit#

The survivors understood that their own race was finished, and spent their remaining years working to save whoever came next. Their instrument was the Conduit, a prototype mass relay the Ilos researchers had built while experimenting with the technology, a back door that linked directly to the Citadel and bypassed its defences entirely. The Protheans had been close to unlocking full mass relay construction when the invasion arrived. (Mass Effect)

The twelve found a way to interfere with the signal that ran from the Citadel to the keepers, the instruction that would otherwise have turned the station into an open relay on command. They travelled through the Conduit, made the alteration, and in doing so denied the next Reaper fleet the instant arrival its designers had counted on. The Conduit ran in one direction only. Vigil believed the scientists, stranded on a station with no food and no water, had starved to death there, and it did not pretend otherwise when asked. (Mass Effect)

The Watcher's Chamber#

Vigil announced itself in 2183 by throwing up force fields that stopped the Mako where it stood, then guiding the intruders down into the archives. Its first reaction was relief. None of the arrivals were artificial intelligences and none showed signs of indoctrination, which meant the contingency had held and the Reapers still did not know Ilos existed. (Mass Effect)

What it gave Shepard was a history lesson delivered under a clock. The Citadel was an enormous mass relay linked to dark space beyond the galactic rim, where the Reapers waited out the long intervals between harvests in hibernation. Activation would put a fleet in the middle of galactic civilisation before anyone could react, and that was precisely how the Protheans had died: their leadership killed before the news of the attack had even spread, their census records and star charts handed straight to the enemy, their colonies isolated and taken apart one by one. Indoctrinated survivors from conquered worlds were passed along as refugees, taken in out of pity, and turned on their hosts when the Reapers arrived. (Mass Effect)

Vigil could not say why any of it happened. It repeated that the motivations of synthetic life had been beyond Prothean comprehension, and that generations of study had produced guesses and nothing firmer. What it could offer was practical. It provided a data file that would grant temporary direct control over the Citadel's systems, told Shepard to find the master control terminal, and pointed out that Saren already knew the route. If Liara T'Soni stood among those present she asked to stay and question it further, on the reasonable grounds that no one might ever get the chance again, and Vigil answered that its programming had been narrowed to information bearing directly on stopping the Reapers. A fuller excavation of Ilos, it allowed, would have been worth a great deal. (Mass Effect)

Silence in the archives#

Whatever power Vigil had left ran out soon afterwards. Expeditions that reached Ilos in the years following found the system shut down, most likely from total loss of reserves, and with it went the clearest surviving evidence that the Reapers were real. The Citadel Council, or David Anderson speaking in its place had the Council not survived the battle in 2183, could point to nothing in the archives that contradicted the official line, and Sovereign remained on the record as an unusually large geth warship. The one witness that had watched the previous harvest from beginning to end had already said everything it was going to say. (Mass Effect 2)