Board Thread:General Discussion/@comment-28962359-20160825041654/@comment-29797245-20160829122347

Here's my theory. I think that you only need a human soul to cross the barrier. Not a monster's soul. The monster's just don't know this, because they are not strong enough to cross the barrier, and the only time somebody crossed the barrier was with a monster soul combined with a human soul. I think Frisk was able to pass the barrier here because of this. Also, why didn't Gaster/Alphys experiment on the other humans with this, instead of letting them be killed? Also, think about it this way: Why would they design a barrier that they themselves couldn't escape?