Saren Arterius

SPOILER WARNING

Saren Arterius was a turian SPECTRE notable for going rogue after being indoctrinated by the Reaper, Sovereign.

When Saren came into contact with Sovereign, the ancient machine was able to convince him (with a little indoctrination) that the races of the galaxy stood no chance of resisting the Reapers, but that the Reapers would allow some of the galaxy's people to survive if they could prove themselves useful to the Reapers. Saren set out to do just that, believing that by helping the Reapers, he could convince them to spare at least some of the galaxy's citizens.