*pants* I-I-I have a... A THEORY!! (Also, Sorry if my writing makes no sense. I wrote this as fast as possible so I wont forget it.)
Today, I was looking at the "dark heart pin" from the Undertale/Deltarune Fan-gamer shop. I read the description and it said: "There is a prophecy. The Angel... The One Who Has Seen The Surface... They will return. And the underground will go empty." Hmm... This sounds a lot like Undertale, right? Yes. It's probably for Undertale and the "dark heart pin" is just for the Deltarune symbol, right? Wrong. If you think of the monsters underground in Undertale as the darkeners in Deltarune, then you'd know that the "prophecy" is going to end with darkness. Kris and Susie jump into a "hole" every time they enter the dark world. They have seen the light. Now, who's the angel? Idk, but what's the angels heaven? The light world. In the end, Kris, Susie, Ralsei (and maybe Noelle) will work together to destroy the Light world. This is why Ralsei doesn't tell us in the beginning about the full prophecy and why Susie "doesn't want this to happen". She doesn't want her world to be destroyed by darkness and have other lighteners fend for themselves in it. So, this is how the prophecy ends: Eternal darkness. They let the Darkeners out the dark world, only to have them transform into stone. The lighteners fend for themselves in the darkness. Their world will end when Deltarune is finished.
