How do you explore the Andromeda galaxy without Mass Relays? Kind of a nit-pick, but it was one of the major technologies in the previous games. Reaper technology guided the development of every species. It was kind of fundamental to the lore of the game. None of the council species had managed to crack the technology behind the Mass Relay. The Programs, who were much more advanced than the council species, had only barely managed to make a one way mini-Mass Relay.