Vigil

Vigil is a Prothean VI (Virtual Intelligence) found on Ilos. Vigil's hologram interface has badly degraded, but his programming is still intact. His personality imprint was taken from 'Ksad Ishan', the Prothean Chief Overseer of the Ilos facility. He helps Commander Shepard understand the fate of the Prothean civilization and the truth behind the Conduit.

Using forcefields to stop the Mako in its tracks, Vigil guides Shepard's team into his chamber in the archives. After monitoring their communications during the operation on the surface, he has translated his output so they can all understand him. He is relieved to see the squad because none of them are artificial intelligences or indoctrinated, proving the Protheans' contingency plan worked. Vigil is desperate to help Shepard and prevent the commander making the same mistakes that the Protheans did.

Vigil explains that, following a cycle that has continued for millions of years, the Reapers returned and began destroying all organic civilizations in the galaxy fifty thousand years ago. They were able to do this using the Citadel itself. The Citadel is the perfect meeting point for all galactic cultures... but it's also a trap. The Citadel is actually a gigantic mass relay allowing the Reapers to return from dark space. Because all the galaxy's major leaders were on the Citadel, the Reapers were able to wipe them out and throw the Protheans into disarray, then use the Citadel, as the hub of the relay network, to lock down all the mass relays and isolate the Prothean systems from each other. It also gave them access to all the Protheans' files, star maps and census data to ensure the destruction was complete.

Prothean scientists on Ilos, however, were saved because the records about Ilos were destroyed in the initial wave. The staff on the planet were preserved in an underground facility that the Reapers failed to find and destroy, put into cryogenic suspension with Vigil to watch over them, so they could be released when the Reapers were gone. However, because of the centuries it took for the Reapers to destroy the Protheans, Vigil was forced to save power by deactivating the cryogenic pods one by one, killing the individuals inside. Most of the Protheans died, except for the top scientists who were brought out of the pods after the Reapers finally left. There were not enough of the scientists to reproduce and save their species from extinction, so they instead tried to save future species. They used the Conduit to reach the Citadel, and interfered with the signal to the keepers that allows the Citadel to become a mass relay. Though Shepard and the squad are horrified that Vigil killed the people he was supposed to protect - hundreds of them - Vigil says that this eventuality was not entirely unforeseen by the Protheans and that he was following contingency planning. The squad is sure the non-essential staff at Ilos didn't know about this 'contingency plan', though.

Vigil gives Shepard a data file that will grant direct control of the Citadel's functions, saying that Shepard must break the cycle of genocide that the Reapers cause. Despite his knowledge about the Reapers, Vigil can't answer Shepard's questions about why the Reapers keep fostering and then destroying organic life: the motivations of synthetic life were beyond the Protheans' comprehension. If Liara T'Soni is in the squad, she wants to spend more time talking to Vigil to learn more about the Protheans from him, saying this might be their only chance. Shepard can tell her off for wasting their time, but even if Shepard agrees, Vigil explains his programming has been limited, and he is able to provide only information directly related to stopping the Reapers. Nonetheless, if Ilos is explored further, Vigil could provide a wealth of knowledge not previously known to the present generation of species.