Fell Papyrus

Origin: Created by or worked with Dr. Gaster; lives in Snowdin with his brother Papyrus.
Personality: rude, aggressive, believes in the principle of "kill or be killed", loves black humor.
Appearance: A skeleton with sharp teeth (one gold), a red glowing eye, bags under the eyes; wears a black jacket with a fur hood, a red sweater, and black pants with a yellow stripe.
Abilities: osteokinesis, telekinesis, gaster blasters, teleportation, gravity magic.
Relationships: with Papyrus - tense (he insults him), towards Frisk - hatred.
Role in the plot: the main antagonist of Underfell, dies in battle with Frisk after 24 rounds (or is "re-educated").

Who: Skeleton, member of the Kingsguard, Sansa's brother.
Height: ~190 cm (6 ft 3 in).
Appearance: Scar on his right eye socket, sharp teeth; black uniform, red cape, red gloves and heels, Bad Boy belt.
History: saved Sansa from Asgore's execution - in exchange, he joined the Guard and received a scar as punishment.
Personality: Cold and ambitious, but devoted to loved ones; loves evil puns, snorts instead of laughing.
Abilities: Bone manipulation (red/sharp/spiky), telekinesis, gravity manipulation, traps.
Relationship:
with Sans - brotherly care behind the facade of sarcasm;
with Undyne - ally and sparring partner;
with Asgore - hates him because of the scar, but obeys;
with Alphys - received high-heeled boots from her.
Fact: Makes delicious lasagna.