The song above is her 1st theme.

This is her second theme:

https://youtu.be/kf692zBUOac

I'm going to rename those two themes just because.

1: Killerovania

2: Time to Strike Back

What Nightmare and Chara look like: 

(Gosh those pics are so blurry sorry) (Also I know it sucks)

Favorite colors: Blue, red, and black.

Personality: She likes to play a prank or 2 on her friends, and she often gets into trouble. If she sees anybody who even LOOKS like the person who killed her family/burnt down her house, she won't hesitate to kill them. She also has that "I don't give a crap" attitude.

Age: 10

Gender: female (well duh)

Powers: She can summon knives and guns. Chara takes control of "Nightmare" whenever she is hurt badly. She's very agile and strong.

Real First name: Angel (I couldn't think a middle name or last name.)