Currently Unnamed Post-Neutral AU.
If you have AU name Ideas, tell me :D
This is based from a playthrough I did right before making the AU.
One Full Year after Frisk left the Underground, 6 humans had already went into the underground, and died. A 7th falls. This starts our tale once more.
Let's start with these 4 Characters.
Flowey the Flower: Your best friend! A little flower who wants to help Charlie get out of the Underground.
Woshy: Woshy is a strange Case. They are one of the 2 Woshuas killed by Frisk. They were awakened by Charlies fall, but have no recollection of how they died. They are the Narrator, taking a role similar to Chara.
Charlie: The final human needed for monsters to be free. Charlie fell down the mountain on a cold winter night, seeking Shelter.
The Last Whimsalot: The last Whimsalot is, well, a Whimsalot. The LAST Whimsalot. Hence their name. They swear to get revenge on the humans who slaughtered their brethren. They live in the RUINS and take a role similar to Toriel, being the boss you face at the end of the Area.
Napstablook is the same ol ghost.
Here we have the (Currently designed) Snowdin people!
Sans the skeleton is the brother of the King. He used to be responsible for the paperwork, but now he's been tasked by his brother to try and lighten up the lives of the monsters underground.
Mew Mew is happily living in her body, now fully corporeal despite Frisk not fighting her in her new form, but still feels a little lost from the death of Undyne. She takes a role similar to that of Papyrus, battling you at the end of Snowdin, then hanging out (Or dating, if you flirt with her.) with you. She lives in Sans and Papyrus's house in the Dog Shrine Room.
Madjick is the Mini-boss who replaces Doggo, due to Doggo being dead. Not much else about them.
Lesser Dog is now the Canine Unit's top ranking member, due to their assistance to the new captain of the Royal Guard, who keeps herself anonymous to the public. She promoted them to Sergeant of the Canine Unit. They appear quite a lot in Snowdin, you fight them only once, though. They are a good dog.
Alphys is the Anonymous Captain of the Royal Guard. She wants to give people hope the same way Undyne did, but believes they deserve to not know who she is. She was going to do what she's heavily implied to have done in some neutral endings, but Lesser Dog was there and stopped her with some Doggy affection. She fights you at the end of Waterfall, taking a role similar to Undynes. She also has a hangout initiated by Mew Mew.
Shyren and her Agent were not Spared by acting, instead, Frisk attacked her and spared from her Low HP. She is very underconfident. Her Agent is trying to help her out.
Monster kid needed a new Role model after Undyne's death, and Father Alvin helped them "see the light of the angel." Monster kid is now wearing their Deltarune Attire, and they appear in Waterfall, attempting to teach Charlie the ways of the Angel.
RG03 and RG04 take the same role as RG01 and RG02.
Muffet becomes the royal scientist after finding out that under one of Papyrus's new policies, it pays well. The Robot is called "Mettaton SP." it doesn't get an EX or NEO form. It's actually just being piloted by one of Muffets spiders. It pretends to be the original MTT, just with a new body. Bpants knows the difference.
Burghley- i mean nerdly- i mean berdly is some little kid who wants to be Muffet's assistant.
Papyrus is the King of the Underground. Because... Process of elimination.
Just SOME Stuff to know about Frisk's run:
Napstablook, Lesser Dog, Greater Dog, Dogamy and Dogaressa, Papyrus, Shyren, Mad Dummy, Muffet, and Flowey are the Unique enemies that were spared. The ending they received was the King Papyrus ending.
Monster they killed the most of: Whimsalot, with a whopping 8 killed.
Non-Unique enemies that they didn’t kill at all: Pyrope, Moldsmal, Jerry, Chilldrake, Migosp, Vegetoid, Whimsun.
So Sorry was not fought at all and technically counts as spared. (Glyde was killed.)
Frisk's LV at the end was 14.
After Frisk returned to the surface, they told a lot of people about the Mountain. It didn't take long for 6 other humans, these ones all adults, to go into the mountain. Frisk had described how they were attacked. They didn't mention how they fought back. The six adults were overpowered by the new puzzles set, and their souls were claimed before the King even knew they were Underground.