it was the year 20XX. You were a child that fell down into the Underground on Mt. Ebott, the place where monsterkind was sealed away by humans after a long, brutal war, you are walking through the Underground, past the final corridor, after getting past Sans. You need to get through the barrier. But someone stops you. It was a goat in a purple robe, crown on head, massive trident in right hand. It was king Asgore Dreemurr, the ruler of the Underground.

Asgore:"greetings, human. It would appear that you got to the barrier. I am going to need your soul along with the 6 other human souls to break it and free monsterkind. So it would be preferable if you just do not resist..."

Asgore said. He is clearly intent on getting your soul. Whether you like it or not. He also broke the "MERCY" button. Now you are FORCED to fight Asgore.