Chara

Chara was also a teen before they fell down Mount Ebbot. They had a tragic sort of nature before they fell down the mountain as well, being called a demon constantly because of the mask she wore. Hockey masks were made for people who had become insane, or were thought to be evil. One day, she had murdered her parents for beating her for taking off the mask. She had gone insane after that moment, she ran off with only half of a heart (figuartively, not literally) to Mount Ebbot to escape humans, and take on a new life. After she fell down, Asriel had become her big brother, and learned that maybe not everything in the world is terrible. Chara has a sort of tsundere, but sarcastic personality to her. Though she isn't often flustered by many people, she may have some sort of crush, but who would know?

Chara's Personality
Hooo boy, if you could describe Chara in one word. It would probably be... mixed. Mainly because of the mix of insanity, regulart teenager, and depression emotions that have been with her since the beginning of her new life down Mount Ebbot.

Chara's... Second Self
"Wait... Chara has a second self? WHAT THE HELL DOES THAT MEAN?!"

Basically after she absorbs a soul in the True Pacifist Run, she becomes more gentle, hence becoming sane yet again.