Wholehearted Half-Souls

Chapter 0: The Tale of Undertale

Long ago, two races ruled over the earth: humans and monsters. They lived in peace and harmony for centuries until discord became sown between them. This was cause for a great war between both races in which the humans were victorious. The humans sealed the monsters underground with a magic curse. No human who ever visited the depths of Mt. Ebott returned alive until one child changed that.

Frisk, a lonely 10-year-old wanderer, fell down Mt. Ebott and discovered the monsters all trapped underground by the barrier. Despite their scary appearances, the monsters befriended the human lad, and he felt a bond with them that he had never felt before. He desired to break the barrier and free the monsters during his journey, but the opportunity refused to align.

However, there was hope. A creature by the name of Flowey, a nefarious flower who had intentions to harm Frisk at every turn, took the human souls except for Frisk's and all the monster souls, placing them into his body. Through this, he became his true form: Asriel, the once passed-on prince of the king and queen of the Underground, Asgore, and Toriel. 

While trapped in his Flowey form, the deepest essence of his being, his soul, was absent from his body. He couldn't feel love or compassion. Thus, destroying everything was the only logical conclusion for him. However, through Frisk's sympathy and care for Asriel's plight, things turned on a dime. Their rivalry began to blossom into a friendship. 

Frisk recalled Asriel's life and all of the twists and turns. Not only that, but the lack of SOUL was hard to experience. Frisk understood this. By researching the true lab tapes found in the deepest, darkest depths of the Underground, Frisk realized the truth. In learning the truth, he forgave Asriel for his deeds, and Asriel repented of his sins against all monster-kind. Using the power of the six human souls, along with all the monster souls he had, the barrier had been destroyed. 

With the barrier now removed, both Frisk and the monsters were now free to leave the Underground and return to the surface once more, and Asriel was redeemed and became the greatest hero in monster-kind's history. 

However, without a soul within his body, Asriel knew what was coming. He would return to his flower form and be trapped in the Underground. While he was thankful for his redemption and felt at peace, a heavy burden still lay on the little goat monster's heart. After giving a heartfelt, tearful goodbye to Frisk, Frisk and his companions left for the surface. At the same time, Asriel returned to his Flowey form and continued to live in the Underground of Mt. Ebott indefinitely. He wasn't sure if he would ever regain his real body or permanently reunite with his parents. Despite the positive change, things simply were not the same.

Until one day, a year after the monster race was introduced to society once again, Frisk and the royal scientist of the Underground formulated a plan. This plan involved a family reunion. Out of all the different monsters, there was one monster who Frisk felt a fondness for the most. Despite only knowing this monster for a short time, his compassion for this friend was so great that he could not leave him behind. Again, this monster remembered was Asriel. 

Frisk knew what he had to do next, especially being the ambassador of monsterkind.

On the selected night, a nearly 11-year-old Frisk returns to Mt. Ebott. Slightly taller and thinner, yet while still being short and fairly chubby, he still has the same calm yet neutral demeanor on his face. As his purple and blue-clad figure runs up the back of the mountain into the cavern not far above ground level, he rediscovers where the barrier used to be. What used to be a large, white shield covering the entirety of the cavern hole is now free of any object, easily revealing a narrow passage that leads to a dilapidated throne room.