#disabled au

Horror isn't totally mute, it's more like aphasia than mutism, which means he has trouble speaking and finding the right words and is practically incapable of forming a full sentence, he also has trouble reading and, by extent, writing.

He became aphasic after Undyne's spear impaled his skull, which obviously caused a lot of brain damage and particularly in the area in charge of the speech, reading and all.

When he joined the bad sanses nobody noticed his struggles at first, they already had Dust who didn't talk much (he isn't mute, just doesn't talk a lot) so they thought he was just the silent type like him. But it soon became clear there was a broblem when he started mixing up words whenever he tried to speak, couldn't decipher written instructions or struggled to write his reports.

However they first thought that maybe he didn't know how to read/write, but it wasn't logical as he was still a Sans, so that meant he was a scientific in his youth, that he must have known how to read and write, so the problem might have been something else entirely.

Surprisingly it was Killer who came up with the first hypothesis, one of which was that Horror was dyslexic, which was close, but not quite that. After some time and researches they eventually managed to find out he was aphasic.

At that point Dust took the responsibility to teach everyone sign language, since he was the only one knowing it at the time, so that Horror could communicate easier and the others would understand him. He still has troubles sometimes with hand placement but he can now communicate !

As for the instructions, Nightmare gave him a magnetophone so he can hear them rather than read them. For the reports it's usually Killer or Dust who write them for him, he signs what he wants them to write and they translate.

On the fluffy side, they sometimes read him stories since he cannot read them himself.

Now for the additionnal headcanons that have nothing to do with disability:

- he likes woodcarving, he often sculpts little animals and give them to each member of the gang (including Nightmare) to show his affection towards them, they are very pretty !

- he cannot see pictures in his mind, I don't know how to describe it but like when he thinks about an apple, for exemple, he doesn't see an apple in his mind, he has the concept, the word, he knows what it looks like and can describe it but he just doesn't visualize it. Same when he sleeps, his dreams are made of sounds and sometimes shades of lights, but no images (aphantasia)

- his pupil will round up like a cat when he sees something or someone he likes