This has been a question that i wondered a loooong time ago. If classic sans dies. What happens to the other AU's? Nothing?
Yup, absolutely nothing.In Underverse, there are only two persons who are the “heart” for each AU (This only applies in AUs where both or one of them exists.)
If both, or one of them dies, the entire AU with their respective timelines could start to collapse.
Also, if someone dies outside of his world, he won’t return to his timeline, no matter how many resets has been made, they will cease to exist.
And just as an aditional info: Pacifist timelines are actually an easiest way to take control over the other timelines (neutral, genocide…) until control and alterate the entire Alternate Universe.
Why does this remind me of the wreck it ralph sonic thingy? :O