The Keepers are a race of aliens from a long forgotten planet that suffered its own 'Event' over 100 million years ago.
Their technology has expanded to such an extent that their spaceships can teleport instantly to any point in the galaxy, though the engines do have to cool down for a few days before this can be done again. They have unmatched medical and dietary science that would hurt a modern human's brain to think about. They have also discovered ways to prolong their lives indefinitely, so almost all of them now are millions of years old. The main issue is that these methods are extremely detrimental to the reproductive system, rendering them predominantly sterile.