Originally Posted by akbar
He is what spread the toxin so no one could inhabit the planet. The design was for them to leave the planet (a testing facility for weapons) with their harvest. But they crew ran out of time before the "virus" ran its course and they could make it to the ships. The "architects" that were found outside the containment areas were supposed to be launching the ships but the virus spread so quick (thanks to the water) that it consumed the planet and attacked them. The only place for them to hold up was in the containment areas and hence the "architects" still in hypersleep pods at the end of the movie.