Chara is a female human child. She run away from a humans and fell to the Underground and was adopted by royal family.

Chara is wearing a lime and cream-colored striped shirt and red-brown shorts.

Chara has peach skin and brown hair, rosy cheeks, brown eyes, and an unsettling smile.

Chara is often talk and act rude, sarcastic and sadistic.

Dr. Alphys is a female, reptilian monster that lives in the lab in western Hotland. Alphys is the incumbent Royal Scientist.

Alphys is a yellow, reptilian monster. Alphys' posture is somewhat hunched over. Alphys has yellow scales, claws, and protruding teeth.

Alphys is a nerdy, shy recluse with a fondness for human anime and manga.

Alphys often makes clothes and toys for Chara's and Asriel's 'games'. She believe they share her passion for cosplay.

The Laboratory is the workplace and home of the royal scientist, Alphys, in Hotland. It is a single building of technological prowess where Alphys conducts her studies. It also houses the True Lab. The Lab is a large white and red building with a pale green interior. There are two floors on the lab, the ground floor being Alphys's workplace, and the second floor being her room.

Monsters are a very diverse race in Undertale. They dwell in the Underground beneath Mount Ebott.

King Asgore Dreemurr rules all monsters in the Underground. After The War of Humans and Monsters, the humans from the Surface trapped the monsters underground. Monsters are far weaker than humans.

Toriel is an Asriel's mother and Queen of Underground.

She is a monster whose head resembles a white-furred Nubian Goat, structured with droopy ears and short horns. She has a pair of visible fangs and long eyelashes, and her irises have a dark red tint. She has an anthropomorphic body, with paws at the end of her limbs.

She wears a long purple robe that displays the Delta Rune on her chest.

Ancient glyphs adorn walls throughout Waterfall. The color palette of this region is mainly purple and blue with the occasional black abyss. Mushrooms, Echo Flowers, gems within the walls, and water in some areas glow bright blue. True to its namesake, pools of water often provide the atmosphere in Waterfall, and the ceiling drips with water in some areas.

Underground is a large region underneath the Surface of the Earth, which houses the kingdom of Monsters. The exit from the Underground is blocked by the Barrier, which was placed by the Humans ages ago. Spanning several different climates, the Underground features the Ruins, the cold and wintery Snowdin, the wet and cavernous Waterfall, the blistery and barren Hotland, the technologically advanced CORE, and the Capital.

Asgore Dreemurr is the ruler of the Underground and its denizens, monsters. He is the husband of Toriel and father of Asriel.

Asgore is a anthropomorphic goat-like monster with broad shoulders, a bulky body, a golden blond mane/beard and two large curved horns.

Asgore wears a suit of armor, a purple cape with golden pauldrons, and a crown on top of his head.

The weapon Asgore uses in battle is a long, red trident adorned with a flower.

Asriel Dreemurr is the child of Toriel and Asgore and the adoptive brother of the Chara.

Similar to Toriel and Asgore, Asriel has long ears, soft white fur, short tail, a round butt, a snout, a visible fangs and a tiny penis. He has a small wisp of fur on his head and have tiny barely visible horns.

Asriel is a docile, unadventurous, and loving child.