Board Thread:General Discussion/@comment-31270796-20170326200357/@comment-26887879-20170331180052

I think that, "all" is just a rough explaination used to point out how much human soul is stronger than monster one...

Also, many other monsters died/were born in the underground other than Asriel and Gaster. Monsters also have their death rituals. "Falling down" is actually a state in wich monsters that are about to die(from natural death) are in (they were also Alphys' guinea pigs that ended up as amalgamates).