Protheans (Earth-1791)

The Protheans are an ancient sentient species which mysteriously vanished over 50,000,000 years ago. The Protheans arose from a single planet and developed an immense galaxy-wide empire encompassing many other spacefaring species. Not much is known about them, but many of their artifacts, ruins and technology have apparently survived the ages, including the Halo Citadel, the Halo Array, the Mass Relay Technology and the Ark. Prothean artifacts, therefore, have immense scientific value and are seen to belong to the whole galactic community.