Undyne

Dr. Undyne is the Royal Scientist of the Underground and the owner of Napstaton.

Appearance
Undyne is a blue, anthropomorphic fish monster of similar height to Papyrus. She has scales, square glasses, and wears a long white lab coat. She has short red hair that is in a bun.

Personality
Due to the script ending, when Undyne's section began, her personality has never been set in stone.

However, from other sources, it can be inferred that Undyne is an insane/mad scientist who enjoys experimenting on Monsters and Humans. She is also sadistic. She, like Alphys, may also be involved in eating human flesh.

Powers and Abilities
Undyne's Powers have never been stated. Though, she is commonly seen using physical weapons, such as scissors and saws.

Napstaton
Undyne is the owner and creator of Napstaton.

Alphys
She is the current girlfriend of Alphys.

Chara
Chara was brought to Undyne's lab by Alphys, where she most likely would had done experiments on Chara.

Temmie
Though Temmie and Undyne don't have a direct relationship, it is depicted that Temmie was(technically)created by Undyne because Undyne injected Determination into Temmie(Undyne is unaware of this).

Toriel
She might be working for Toriel.