the world has been taken back, the population rebuilt. Well, mostly. They've sealed off the reaper holes and made sure all those things were gone for good. Nina, and Will still mourn Katie ever since she died in the mines, that's when they got news that something new was rising from the repeat holes. Vaguely resembling humans, but vaguely resembling the reapers as well

Nina and Will went down a reaper hole to investigate what was going on