"Hey there. I was told that I was supposed to kill you, but I don't really feel like it."
– Undyne, when talked to in Grillsy's.
In Underground, Undyne is a laid back, compassionate monster with incredible strength. She has the Judge role.
Undyne is the second in command under the Royal Guard, and typically follows the orders of Impact, unless she disagrees with them. She prefers to solve conflicts non-violently, but enjoys sparring as long as both parties are willing. Undyne has connections with every monster in the underground, and usually is friendly with them. She has a crush on Alphys.
She can be considered the strongest monster in the underground, due to her high stats, powerful attacks and mastery of soul-changing attacks, aswell as her refusal to die.
Undyne wears a red, puffy jacket with white sleeves, a pair of rolled up jeans, and red sneakers. Her left eye is typically covered by an eye-patch, and if the eye-patch is removed, reveals an eye that flashes orange and violet, similarly to canon Undertale Sans. She typically wears a modest, calm expression.