ZenTale (Undertale AU)

The Beginning

 Long ago, during the war between Monsters and Humans, a skeleton scientist named W.D. Gaster and the original Lich Queen of the Underground had two children. These children were born in order to keep balance in the Universe and guard it from those who tried to harm it. Sans, born of the Yin aura, held hope in the darkness he was born from and cursed with bad luck. Papyrus, born of the Yang aura, held doubt in times of good and was blessed with optimism. However, the severity of the power was too great for their mother to bare, killing her in the process of the birth.

This greatly crushed the mental state of Dr. Gaster, and even after hearing the news of the Humans being defeated for the first time in ages, the crushing blow of no longer having the military strategist and a Queen, the Humans pushed the Monsters back into the Underground with one final retaliation. Blamed for the murder of their Queen and illegal experimentation. Gaster and his sons were cast outside of the kingdom into the Deep Underground where Gaster had begun the next phase of his research. First, Gaster was going to test how close the bond of the fraternal twins was. He put them together in a room with toys and books, studying them for days. Sans, the eldest of the two, took more interest in books, especially those that revolved around science and magic. He quickly learned how to use Soul Energy to use different types of magic, most of them being offensive types. However, Papyrus, the youngest twin, had taken more interest in the physical items and trained his body. His intelligence was fairly average and was extremely optimistic. He quickly learned how to develop fighting stances, both offensive and defensive.

Gaster, quickly gathered this data and smiled at how different they were, and that neither needed to depend on each other, until the next day when the two officially interacted as individuals.