Betty Noire

Bete, under her human alias, is a curious child bursting with energy. She acts cheerfully and is quick to greet peers with a huge smile. Nevertheless, despite appearing sweet and innocent, Bete's false personality quickly dissipated after Asriel and Sans discovered some AMD camera footage of her acting rather suspicious. During this time, Dr. Gaster learned that Agate Lightvale sacrificed her own soul to create a powerful creature that would make sure monster-kind and humanity never live in peace. Afterward, Bete revealed her true personality, quickly indicating that she enjoys it when she severely hurts others (both physically and emotionally), showing that she has a very sadistic, psychotic, and violent personality.

She appears to enjoy hurting her opponents before she kills them. In fact, Bete is known for attempting to kill anyone in her way. It's also clear that she has no problem lying to, or betraying, others, as she manipulated Jessica into doing what she wanted them to do. During combat, she often becomes arrogant, resulting in her underestimating her enemies. She also displays minimal tactical knowledge, allowing the use of strategy to defeat her in battle, as shown in her various battles with Gaster Although it is observed that she can calculate and knows how to get what she wants, though she seems to not be able to plan to a great extent.

Bete, for the most part, believes what she is doing is right. According to her conversation with Akumu, and a couple of lines from Scared Of Me, she believes that monsters and humans living together is "like a time bomb waiting to go off". Therefore, she thinks that what she's doing is "just speeding up the process",

While under HATE's control, Bete acts far more violent and frightening than she had previously. In this state, mostly during combat, she mercilessly attacks her foes with a menacing grin. Also, Bete seems to be scared of HATE's plans, as it could control her; this means she knows that HATE has different plans than her own. Without a doubt, Bête Noire's biggest (and even fatal) flaw is her arrogance, and this mostly likely stems from Agate's own arrogance after she killed her brother.

Occasionally, Bete shows care for Akumu and talks to it as an acquaintance. For example, in Do or Die, she seemed concerned when Akumu was hurt in their battle with Gaster. Both Kumu and Bete treasure each other like their best and only friend, but regardless of this false hope, Cami said it was a kind of instinct since they need each other to live. If one of them dies, the other slowly dies due to the lack of magic and inability to collect souls alone.

Betty physically appears as a preteen girl with medium length, two-tone, brown/pink hair. She wears a magenta skirt with torn edges, a light purple turtleneck with a large light pink stripe at its bottom, light purple leggings and knee-length brown boots.