Ruins: the story begin with the human fall , the human hate monsters knowing about the war tough that monster attacked , when it first fell in the underground the human start with a killing spree , unlike Undertale here flowey try to actually kill him / her destroying the soul , this grow unsuccessfull as the end his head get cut off , the ruins have complex puzzles and strong monster , monsters are aware of the human killing spree and try to make the ruins stronger and safer by reforcing them and attacking in group , we can say the ruins create a true base for the monster ( tou we can’t call them ruins as the ruins are replaced by a a new area called temple ) this place have trap ideated for kill this treath , toriel know about this and help the weakest monster to escape instead of sitting there and waiting for the human , the ruins have a minor guardian that take instant action in the treath , after killing him the determination point become red , these would be various scenes of actions and overworld fighting instead of only Undertale battle style .

In the toriel house toriel would wait for you at the end of the temple , but seeing you remember her about the other humans and she give you one last chance for turn back , in that moment the human attack and....https://youtu.be/B6gmEfXeS5w this happen ( very old intro , we are remastering it , this was when we still used clickteam )