Storyverse[]
Storyverse is where Toriel stops Asgore's plan to get the 7 human souls. Then she became the ruler of the underground and made a new policy, all humans that fall should be treated well and become friends. Everyone respected her rule, some others didn't.
Flowey was mostly the one trying to kill the fallen human, others just through that they should have a right to go to the surface. So some others do the same, but they are trying to replace themself like Asgore, so they could break the barrier and become a god. However, if they kill the protagonist, they still need 6 more souls.
The protagonist is able to get past these monsters because they are too easily determined. And if they ever need help, the protagonist can call for help and one of the main characters (besides Toriel) will save them from the threatening monsters.
Sans, Papyrus, Undyne, and Alphys all help the human all the way. These characters will help the protagonist get past anyone rude who gets in the way.
Toriel put the human soul in a place where no monster can find it. What is she going to do to the souls? Well, she wants the right moment to break the barrier and free the monsters.