They don't control them. The worms grant the hive prolonged live and feed on their ambitionsin exchange. This way the hive have to improve constantly. You could say the darkness brought some kind of golden age to the hive, it's vastly different from the travelers version though. As for who started it: there was a natural disaster that caused massive gravitational waves to destroy the region where the hive originated from. IIRC the worms said the traveler caused it to destroy them, while the traveler said it was a lie by the worms the deceive the hive in order to make them join forces with the worms. As in the original post stated: good and evil are relative. Who knows which side speaks the truth.