Undertale

The Dungeon is a vast cavern beneath Mount Abbot, home to monsters. It's a fiery cavern with various locations: the Ruins, Snowdin, Waterfall, Hotland, the Core, and New Home.

"Ruins" - despite the name, it is not ruins, it is a town with purple houses, and there are also some puzzles. Toriel settled in the Ruins after leaving Asgore.

"Snowden" is a snowy location with forests and a town called "Snezhnegrad," home to furry monsters. The town features a hotel where you can relax, a shop where you can buy things, a library, and a bar/diner called "Grillby's." Sans and Papyrus live in this location.

"Waterfall" is a beautiful location with numerous waterfalls and lakes. Undyne lives here.

Hotland is a hot location, and accordingly, heat-loving monsters live there. Hotland is home to Dr. Alphys's laboratory. Hotland is also home to Mettaton's enormous, opulent Hotel. Hotland is also home to the Spider Commons, where Muffet lives and sells her spider concoctions. Elevators allow you to travel around Hotland.

The "Core" is the heart of the dungeon, the building you can enter.

"New Home" is a gray city with Asgore's castle at its center. Asgore named the city because he's terrible at coming up with names.

Resolve is the force that allows people's souls to continue to exist after death. It can also be the name for a person's soul.
Determination is a natural quality in all people.
The only monster that has confirmed determination is Undyne, but it is possible that every monster has a small amount of it.
Some characteristics of determination: If a monster gains a high concentration of determination, its body begins to melt, typically turning into amalgamation. A creature without a soul can gain the will to live if it gains determination, a prime example being Flowey. Save points, located throughout the Dungeon, express a person's determination, restore health, and also reflect their thoughts. They appear as four-pointed stars of bright yellow or gold.

Battle mode - when a person encounters or starts a battle with a monster, the person switches to "battle mode" or "soul mode" in which you can either kill the enemy or spare him.
During the battle, a person becomes a small heart, which symbolizes the human soul.
Selecting a monster to attack.
A human can attack or interact with one monster each turn. The human acts or attacks first, then the monster attacks, and so on in turn. In "battle mode," the human must dodge the monsters' magical attacks.
Attack Aggressiveness - The aggressiveness of monster attacks changes depending on how a person interacts with them: if you do not use violence, then it will be easier to dodge attacks, and vice versa.

There are four buttons in total: "BATTLE", "ACT", "THINGS", and "MERCY" that a person can use in "battle mode":

"BATTLE" — a bar (there may be several) appears and moves across the indicator. To perform a strike, hit it when the bar is as close to the center of the indicator as possible. Damage inflicted. To deal increased damage, you need to hit the exact center of the indicator, as hitting the edges will reduce damage or miss.

"ACT" - a person can use non-violent methods of conflict resolution (talk, use objects, run away, show mercy), or hit back).

"THINGS" is a strategic button that allows you to use items in your inventory.

"MERCY" - allows you to end the battle peacefully, but many monsters cannot be spared immediately and you must use the "ACT" button first.

Frisk is a 12-year-old human gender-neutral child.
Personally: Frisk has a neutral character.
Soul: Determination (red).
Appearance: Frisk appears as a yellow-skinned human child wearing a blue sweater with two purple stripes, blue pants, and brown boots. Frisk has straight, medium-length brown hair with short, choppy bangs and a consistently neutral expression.

Chara is a 12-year-old demon-human girl who returned to life after the genocide committed by Frisk in another timeline.
Personality: Chara is serious and nerdy, but rarely kind or sociable. Chara loves knives and has a strong love for chocolate.
Soul: Determination (red).
Appearance: Chara has the appearance of a human child. She has peachy skin, medium-length brown hair, and pink cheeks. She wears a green sweater with a long, wide, horizontal yellow stripe. She also wears brown shorts and brown boots.

Flowey is a sentient golden flower with a white center, six yellow petals, and a light green stem. He can distort his face to imitate the facial expressions and voices of other monsters and humans.
Personality: Flowey initially appears to be a friendly and polite flower, but this is used to manipulate his interlocutor. Flowey's idiology is "kill or be killed."
Flowey has no soul, so he is incapable of feeling compassion or love.
Abilities: Flowey has magic and is able to summon his plant-based magical attacks during "battle mode" or just like that.

Toriel Dreemurr — Toriel is a monster resembling an anthropomorphic Nubian goat with drooping ears and short horns. She has two visible fangs and long eyelashes, and the irises of her eyes are burgundy. Unlike real goats, Toriel has paws rather than hooves. She wears a purple robe with white sleeves and a Delta Rune on the chest.
Personality: Toriel is kind, caring, and motherly.
Status: Toriel is the former queen of the dungeon and Asgore's ex-wife but she left him.
Abilities: Toriel has mastered fire magic.

Asgore Dreemurr is a large monster resembling an anthropomorphic Nubian goat with two large curved horns, a golden-blond mane and thick beard, white fur, long ears, and a muzzle. He wears a small three-pointed crown, golden shoulder pads, and a long purple cloak, which he often uses to cover his armored body. Personality: Asgore is kind, quiet, and optimistic. Status: Asgore is the king of all monsters in the dungeon. Weapon: Asgore's weapon of choice is a sharp red trident adorned with a six-petaled flower at the base.
Abilities: Asgore has mastered fire magic.

Sans is a short, smiling skeleton with a round skull. Sans wears a blue zippered jacket with a fur hood, black shorts with white stripes, and white slippers.
Personality: Sans is lazy, a jokester/comedian, and often makes puns (which often irritate his younger brother, Papyrus). Despite this, Sans is caring and can punish a bad person by calling it "bad timing."
Traits: When Sans is serious, his eye sockets are completely empty. And when he uses telekinesis in "battle mode," his left eye glows yellow and blue.
Abilities: Sans has bone magic during "battle mode" Sans can summon bones, use "gaster blasters", telekinesis, and he can also find out what UR and OP a person has and immediately understand whether the person has killed monsters or not.

Papyrus is a tall skeleton with an anatomically imprecise skull structure (compared to his brother Sans's round skull). His mouth is almost always smiling, and his pupil-less eyes resemble vertical slits, with expressions conveyed by his pseudo-eyebrows.
Personality: Papyrus is a hot-tempered, loud, and charismatic skeleton who hates his brother Sans's jokes and puns. He has a catchphrase, "Nya-ha-ha," which he often utters. Papyrus dreams of joining the royal guard, but so far, it hasn't worked out.
Abilities: Papyrus has mastered the magic of bones and can summon magical bones during "battle mode" and can also switch a person's "soul mode", coloring their soul blue and at this moment the person's soul has gravity and can only jump.

Undyne is the leader of the Royal Guard of the Dungeon, and is responsible for tracking people.
Personality: Undyne is feisty, strong, and brave, but she's also madly in love with anime, just like Alphys. Undyne also has a crush on Alphys.
Appearance: Undyne is a fish-like anthropomorphic monster. She has light blue scales, red hair tied in a ponytail, red and blue fins on the sides of her head, red spots on her eyelids, two protruding sharp yellow teeth, black vertical pupils, yellow sclera, and a black eyepatch over her left eye. Undyne is missing a nose.
Armament: When Undyne is on a mission, she wears her grey shiny armor with a helmet, and her weapons are infinite energy spears.
Abilities: Undyne can, during "battle mode", repaint a person's soul green, and at this moment the person's soul cannot move from its place and can only defend itself with the spear that Undyne gives it to reflect her flying spears from four sides: left, right, front, and back.

Alphys—full name Dr. Alphys—is the royal scientist. Personality: Alphys is insecure, often stutters, and loves anime.
Alphys has a love interest in Undyne.
Alphys also created a robot TV star named Mettaton.
Appearance: Alphys is a monster that looks like a small yellow hunchbacked dinosaur with a short tail and an elongated face, wears round glasses and a lab coat.
Abilities: Alphys never engages in battle with a person because she is afraid or shy, which is why it is unknown what kind of magic she has.

Muffet sells spider baked goods – spider donuts, croissants, and spider soda.
Personality: Despite her outward politeness and courtesy, Muffet comes across as a greedy, stingy, frightening, and somewhat hypocritical spider. However, she cares deeply for the spiders of the Ruins, so she donates the money she earns to saving them.
Appearance: Muffet appears as a beautiful anthropomorphic spider with periwinkle or lavender skin, five dark purple eyes, and black fangs protruding from her mouth. Muffet has six arms and two legs.
Wears: a burgundy blouse with puffed sleeves, slightly lighter pants, and a red ribbon around her chest. Her black hair is tied into two small ponytails.
Abilities: Muffet can color a person's soul purple, which allows the person to move between the three threads and dodge Muffet's attacks.

Monster Kid is a young monster, a fan of Undyne who dreams of seeing his idol in action. Appearance: A small, armless, yellow monster with "spikes" on his head. He wears a striped yellow-brown poncho and brown boots. He has spots under his eyes, one slightly larger than the other. Personality: An innocent, extremely enthusiastic, and energetic monster. He's quite inattentive, so he often trips and falls. This is possibly due to his lack of arms for balance.
Some characteristics: Frequently uses words like "come on" or "come on" ("dude") and "yo".

Temmies are cute creatures that are half cat and half dog.
Personality: All Temmies are kind, sweet, and good-natured. They sometimes slur their words, lisp, and mispronounce them. Temmies love to pet people, but many people are allergic to Temmies. Temmies also love Tem Flakes. They live in a hidden Temmie Village somewhere in the Waterfalls.
Appearance: All Temmies have round heads, cat-like bodies and paws, and two pairs of ears on their heads. One pair of dog-like ears is located on the sides of the head, while the other pair of cat-like ears is located on the top of the head. All Timmies have black hair and wear a blue shirt. Timmies walk on all fours.

Froggit is a monster that looks like a frog.
Vipson is always crying and sensitive to battles.

Lux doesn't like being teased because of his last name.

Vegetoid - looks like a large live carrot.

Migosp is a child-sized, insectoid-like monster that loves kindness and being itself.

Snowdrake is an incompetent comedian.

Ice Hat - made of snow, he is a daffodil and shows off his ice hat.

Giftrot - this monster looks like a deer,

Jerry is a monster that everyone hates.

Aaron is half horse, half seahorse, he is a rocking horse.

Voush - a turtle-like place on the shell, a round aquarium in which a duck swims,

Minijell is a living jelly.

Megajell is a tall, jelly-like spring in the form of a spiral.

Vulkin is a lively little volcano who loves hugs.

The wick is similar to a bomb with a wick that looks like a spring and acts as legs.

Tsundereplan is a monster that looks like a living liner the length of a human and acts like a tsundere.

Menzhik is a small monster-magician, he often says magic words like "abracodabra" and so on.
Final Froggit - A monster similar to a more powerful version of Froggit, it seeks the meaning of life.

Vipsilot is a stronger, more warlike version of Vipsone, and knows the meaning of honor.

Ostrematism is a round monster with short arms and legs, he has one big eye, he is a bully and wants to be teased and always achieves this.

The Knight Snytser is a large armored monster who always wants to sleep. She is a girl.

All the simple monsters that were in all the previous locations live there.