User blog comment:The Milkman/The Next Effect/@comment-4737548-20121123020348/@comment-24174486-20121123031425

The Reapers never sought Synthesis. Saren served the Reapers because he believed that assisting them in their plans would convince them to spare galatic civlization—and the Reapers used that belief to manipulate him. Saren wanted exactly the same thing Shepard did, to stop the Reapers' cycles; the main difference was that Shepard wasn't indoctrinated and Saren was.