As a Moments subpage, all spoilers are unmarked as per policy. You Have Been Warned.
Frisk wondered if even he noticed or if he was changing himself deliberately, perhaps it was a way to rid himself of the past.
“You were my home...”
—Frisk
Monster in the Mountain isn't an Undertale fanfiction without Asriel’s tragic circumstances. More so in that it touches on the painful consequences of Asriel's "victory" on both Frisk and himself.
- We now know why Frisk climbed the Mountain: the day they fell, they and their parents suffered a car crash. The parents died, while Frisk ended up wandering up the mountain until they fell into the Underground and found a new family in the monsters. Even that is taken away from them by Asriel when he stole the monsters and wiped a year of their life away. The only reconciliation is that Frisk's aunt was able to foster them in this new timeline.
- The trauma of witnessing Asriel destroy the Earth, and learning that he did it thousands of times, caused Frisk to never want to go to space ever again. An entire universe to explore, of which they were only able to experience a fraction of in chapter 22, and now Asriel's actions ensures they'll never get to see more.
- Chapter 23 finally reveals what caused Monster in the Mountain to diverge from Undertale: it's a Post-Pacifist ending gone wrong. Unable to tolerate his powerlessness and inability to feel, Flowey stole the souls of six dying children and was in search of a seventh the day he was caught by Frisk and the monsters. Overwhelmed by the presence of the monsters, Flowey used the monsters as a substitute in desperation like last time, and then wiped out all memories of the past year from Frisk and humanity as a whole.
- Even if they were unable to remember it at the time, Auntie Ligaya's account of Frisk's return from the mountain implies it was a very emotionally traumatizing event that transcended Asriel's memory wipe, made worse in that their memory now begins the moment after the death of their parents.
- Asriel's Significant Wardrobe Shift isn't just an aesthetic choice. It was a gradual change to his appearance made over centuries with his robes degrading and his physical appearance twisting to reflect his depressed state.
- Flowey didn't even try to do this out of malice. He sought children who were already dying to keep his hands clean, and found that telling them the truth about his tragic background was the most effective means. All he wanted was to give Frisk and the monsters a nice surprise.
- In spite of all the misery his decision brought him, despite all evidence that he truly, genuinely, greatly loves Frisk with all his heart, Asriel could not let go of the souls in chapter 23. The trauma of becoming a flower, and the fear of monsters vilifying him for all his actions, overpowered his love for Frisk, almost severing their relationship and ensuring their child will grow up with a single parent.
- The worst part is that Asriel is fully aware he could just swap the monster souls for a seventh human soul, and knew of the solution for a very long time, but he is so terrified of facing them after everything he did, he simply cannot bear to carry it out.
- This was Asriel's last chance at reconciling with Frisk. He can't turn back time to before their meeting anymore, else he would erase his own child for good.
- Chapter 24 is told entirely from Asriel's perspective. Combined with his interactions with Frisk, it's abundantly clear that Asriel is a deeply depressed and broken individual. For as long as he was a god, he had no one he could connect to for centuries, and humanity could never empathize with him, either seeing him as something to worship or hate, not someone to love as a person. He hasn't even received a hug since he was a child.
- It also becomes clear his actions are as much a Zero-Approval Gambit as his fear of the monsters' scorn. He loathes himself so much that a part of him would feel vindicated if Frisk hates him and raises their child to be a better person than he ever could.
- Even so, he immediately despises his decision. And when Frisk sings "Don't Forget" to him, it causes him to completely break down. Having rejected Frisk, he will have destroyed the last relationship with a loved one. He is now completely, and utterly alone.
No one was coming to help him, not anymore. He just wanted to disappear. There was nothing left for him anymore. - Ultimately, the sacrifices and harm he inflicted was for nothing. Being from a similar timeline as Growing Pains, we learn that, had he stayed as Flowey and gone to the surface with Frisk, he would have had an honest relationship with Frisk and a supportive and loving family. Instead, Asriel had wasted centuries trying to find an alternative, becoming increasingly more depressed until he could no longer deny his love for Frisk nor the agitation of the monster souls.
