So, you know what I’m here to talk about: the story.
Can’t really tell a lot of the story, but it is not like it matters, since I currently have to re-write, re-plan and re-do almost everything. It is not a matter anymore of doing it or not, but instead of when.
I expected Deltarune to change the entire lore I knew, but not really, however I won’t explain why though because Deltarune is still a bit fresh.
Anyways, I will however say a few things to expect:

Toriel: Toriel is kind of psycho or evil in most of the Underfell interpretations I’ve seen around, but here we’ll have it a bit different. She won’t be that evil, but she will be more aggressive due to Flowey following you.

Papyrus: The motives of Papyrus have changed quite a bit, here’s a quote from the 2017 Papyrus:

And here’s a quote about what to expect from the new Papyrus motives:

Undyne: Most notably, Undyne will make a turn from a killer, psychopath or whatever edgy Underfell thing, she’ll retain the few sanity she has to… I won’t risk to say too much about the lore.

That’s it for now. Peace!
-Fell Leader