Ok, so a quick summary. Neutraltale would be a kind of "fusion AU" between Positale and Negatale (like stated above). The story I have for it is Error attacked the duo of AU's leaving them both about half destroyed, and they were too corrupted for Ink!Sans to fix alone so he merged them together and crossed his fingers REAL tight

Basically, the character's have their looks from the AU's merged together like seen above

Also, the monsters don't feel much emotion as most of the Positives and Negatives cancel each other out, so the characters are basically a glimpse of their former selves in the previously mentioned AU's.

That's basically it I think. Do something with it if you want, idc