You learn that this universe has two realms: the “Light Realm” populated by Lightners, and the “Dark Realm” populated by Darkners. The Dark Realm is actually a series of worlds created from Fountains of Darkness, which only Lightners can create in the Light Realm. Both chapters involve Kris and a friend named Suzie, both Lightners, and a Darkner named Ralsei (who looks suspiciously like your brother Asriel) entering one of these Dark Realm worlds and sealing up a Fountain of Darkness. This causes that world to disappear, which is good: If too many Fountains are created, not only will all Darkners turn to stone, but the Light Realm will experience “The Roaring,” an event where giant Titans will come to ravage the land.

Source: Washington Post September 23, 2021 15:22 UTC