Frisk proceeds to (depending on the route) befriend or kill some or all of the monsters. Flowey proceeds to live out multiple lifetimes doing everything he could think of to everyone in the underground (even committing genocide) but later flowey loses his power and a child named frisk who falls into the underground gains the power to control time. Asriel’s new name is flowey and now he has the power to manipulate time to some extent. Years pass and asgore has collected 5 human souls and only needs one more to break the barrier.Sometime in between asriel’s death and frisk’s fall into the underground,asriel wakes up as a living flower however without a soul or emotions. Asgore proceeds to vow that he would kill every human who falls into the underground so he could break the barrier and wage war on humans. Once he returns to the underground he dies on asgore’s flowers. Chara dies but asriel absorbs chara’s soul and becomes powerful enough to go past the barrier and brings chara’s body to their village but the villagers get scared of asriel and attack him. However chara at some point becomes ill and their last wish is to see the flowers in their village. The royal family take care of the child but later, (this is where shit gets a bit complicated as I saw a theory stating that chara isn’t the bad guy until the player who does the genocide route and twists the spirit of chara into being evil) asriel (the son of the king and queen named ashore and toriel) and chara bake a cake but instead of using butter in the recipe they use buttercups and when the king eats some cake he falls extremely ill (some say this was chara’s attempt at assassinating the king, others say this was just a mistake) but the king survives this. One day a small child named chara falls down a mountain and lands in the underground (the home of the monsters).
At some point asgore enlists the help of a royal scientist named W.D gaster to supply power to the underground and gaster builds the core of the underground to supply it with power however, during one of gaster’s experiments he disappears. ( a bit of important context for the story is that monsters’ souls disintegrate after death while humans’ souls can persist after death) Humans and monsters lived in peace but humans realised that monsters could absorb dead human’s souls to become more powerful and after the humans got scared of the monsters’ potential power a war broke out and after the humans won with the superior power of their souls, they trapped the monsters underground with a magic barrier that would take 6 human souls to break.