Toriel

Toriel is a Boss Monster and the guardian of the Ruins, Asgore's ex-wife, and a major character in the story. She is a driving force behind many of the game's events.

Appearance
Her appearance is that of an anthropomorphic goat or dragon. She wears a large, blue dress or robe that displays the Delta Rune on her chest and is occasionally seen with her reading glasses. Her eyes appear to have a slight red tint to them.

Personality
Toriel is a very kind, motherly monster who genuinely cares for the protagonist and their well-being. While ultimately a benign figure, she does have a harder side to her personality, as seen by her refusal to allow Frisk to leave the Ruins and by her cold treatment of Asgore. In addition, she has something of a mischievous streak, evidenced by her interactions with Sans.

Toriel enjoys cooking. Many of her recipes use snails as a primary ingredient, as her favorite food is snail pie. She is also able to bake other things quite well though, as shown when she bakes a cinnamon-butterscotch pie for her and the player (excluding Hard Mode, in which she makes a snail pie in due to lack of ingredients.). She has always wanted to be a teacher. By the time the protagonist reaches her house, she states that she has already prepared a curriculum for their education. This is also illustrated in the game's credits, as she is shown standing outside a school, and in certain Neutral Endings, in which she starts a school.

Main story
Toriel saves the player from Flowey, healing the damage done by the murderous flower. After introducing herself she guides the player through the first few rooms of the ruins. She encourages the protagonist to deal with monster encounters by talking to them.

She gives the player the Cell Phone as they separate the first time in order to keep in contact with one another. Toriel goes further into the ruins, telling the protagonist to stay where they are. She calls them frequently, and is about to call again when she finds the protagonist at her home. Surprised, Toriel shows the protagonist their new room in her home and leaves to finish with the pie she made to celebrate the protagonist's arrival. She leaves a slice of the pie in the protagonist's room when they go to sleep.

Toriel is eager to care for the protagonist, but eventually they ask about leaving the ruins. She leaves for the exit, and as the protagonist follows her, she tells them that she will destroy the exit to prevent them from leaving. This is because Toriel has cared for other humans, and when they left her home, they all died because of Asgore. If the protagonist has befriended Sans, he reveals that he is friends with Toriel, although they do not know each other's names nor have they seen each other in person. Tthey communicate with a door between them. Toriel asked Sans to protect any humans he found, which Sans brings up while dining with him in MTT Resort. Sans remarks that if he didn't make that promise to Toriel, then the protagonist would have been killed (it is not clear if Sans would have killed them himself).

Toriel is revealed to have been the Queen of the monsters, who was the mother of Asriel and the adoptive mother of the first human to fall into the Underground.

Neutral Endings
If Toriel was spared, she will return to rule over the Underground after Asgore's death, bringing in a new policy to treat any humans who enter the Underground as friends: if the player killed anyone then Undyne (or the other monsters) will revolt, forcing her to return to her home in the ruins, but if the player killed nobody then the monsters will accept her policy, abandoning the plan of destroying the barrier as the six collected souls disappeared.

If the player killed nobody and befriended Undyne, then Toriel will be a teacher in addition to being the Queen. If the player also completed the date with Alphys, then Toriel will be checking on Alphys' work (something that Asgore never did), though in the neutral endings she remains unaware of her true experiments.

If the player killed Toriel, depending on which of the other major characters survived, Sans may mention the recent absence of his friend in his phone call to the protagonist. If Papyrus was spared, Sans suggests that she may have fallen ill, but he is interrupted by Papyrus before he can say any more. If Papyrus was killed but Undyne was spared, Sans continues, revealing that he knows the protagonist killed her, and warns them that "things are lookin real bad" for them.

True Pacifist Ending
Toriel appears just as Asgore and the protagonist prepare to fight, using her fire magic to knock Asgore off his feet. She tells the protagonist that she came to stop them from killing Asgore to leave, as it would be wrong to take one someone's life to gain the freedom to leave the Underground. Toriel introduces herself to the protagonist's other friends as they arrive, and she recognizes Sans' voice as her friend. After she stops Undyne and Alphys from kissing, she tells the protagonist that while they may have to stay underground, they may enjoy spending time with their new friends.

Toriel, along with the protagonist's other friends, is bound by Flowey's vines. When Flowey tries to kill the protagonist, Toriel is the first monster to intervene, using her fire magic to block Flowey's bullets. Her soul - along with every other monster's - is eventually absorbed by Flowey, allowing him to become Asriel once more. During their battle with Asriel, the protagonist reaches out to save their friends' souls, Toriel being among them. Asriel uses the souls to destroy the barrier before releasing the souls, and gives Toriel (as well as the other close friends) the knowledge of the protagonist's real name: Frisk. Asriel asks Frisk to take care of Toriel and Asgore, as he does not want them to see him returning to being a soulless flower.

Toriel does not remember much about what happened with Flowey, and she remembers nothing about Asriel. She tells Frisk that they are free to go through the Underground to talk to more of their friends. Meanwhile, Alphys upgrades her cell phone, allowing her to send text messages to Frisk as well as access to the Internet, and she learns about smileys, ASCII and cat videos. Alphys also tells her about her true experiments, leading to Toriel firing her from her position as Royal Scientist.

Frisk leaves the Underground with Toriel and their other friends. As the others leave Frisk to begin their lives on the surface, Toriel asks Frisk what they will do now: In the credits, Toriel is shown welcoming the Monster Kid to a school, having presumably become a teacher. Asgore is shown nearby in casual sun-wear and trimming a hedge, implying they have reconciled to at least some degree.
 * If Frisk decides to stay with Toriel, she remarks that they would have never left the Underground if they made that choice earlier in the ruins, and that it turned out well for them to later change their mind. She understands Frisk has no human parents, and is more than happy to care for them, for as long as they need. She takes their hand as they walk away together.
 * Frisk may tell her that they 'have places to go'. Toriel understands and is not terribly upset to hear this. Before she leaves Frisk on their own, she tells them that she will 'see [them] around'.

What happens after the credits depends on what Frisk decided to do:
 * If they stayed with Toriel, there is a scene after the credits where Toriel brings a slice of pie to Frisk's room.

After a Genocide run, these endings are slightly altered, both having grim implications for Toriel's future.
 * If they went on their own, the screen after the credits shows Toriel and Frisk's other friends together in a photograph.

In Battle
Toriel tells the protagonist to go upstairs, but they refuse and continue to the exit. She blocks the protagonist's way and fights them, telling them to prove they are strong enough to survive.

Choosing Act and then trying to talk to Toriel does nothing; the protagonist is unable to think of any conversation topics, and eventually realizes that talking to her won't help the situation.

The player has two main choices for getting past Toriel: The player can flee from Toriel, but this will not let them leave the ruins.
 * Spare her.
 * One Froggit from earlier warns the player that they may have to repeatedly try to spare someone even if the "spare" text color is not yellow.
 * Missing attacks has a similar result to sparing her.
 * Eventually, she will stop fighting and will only talk. The option to "Flee" will disappear. Continue sparing her to win the battle.
 * Standing completely still will cause you to take damage, however, Toriel will never intentionally drop your HP below 2. Once your HP is low she'll start sending fireballs off to the side, away from the player.
 * Kill her.
 * Another Froggit says that monsters can be spared if their HP is low enough, however Toriel is not one of these monsters; attacking Toriel when her HP is low will deal significantly more damage than usual and outright kill her. Toriel additionally goads the player into attacking her, which combined with the above may trick pacifist players into unintentionally killing her. If Toriel is killed this way, she tells the protagonist not to allow Asgore's plan (which involves taking the human's soul) to succeed.
 * If her guard is lowered from sparing her, attacking once will kill her. She tells the protagonist that they are just as cruel as the monsters outside, and dies laughing.
 * If the player killed every other monster in the Ruins, then attacking once will kill Toriel. She realizes that she was keeping the monsters outside safe by attempting to keep the protagonist trapped, and dies laughing.

If the player dies during the fight, Toriel will put her hands over her mouth in a shocked expression before the "Game Over" screen appears.

If spared, Toriel will hug the protagonist and she will be near the patch of golden flowers at the beginning of the ruins.

Attacks
Toriel has two primary attacks: a sweeping motion with her hands that covers the top half of the box, and a volley of fire balls that stream from the top to the bottom, with a blazing effect on the bottom border.

As the player's health reaches critical levels (less than 3HP), Toriel will stop an attack in progress and begin to purposefully avoid hurting you. She will only use one weaker attack in which the raining fireballs move away from the player's soul. However, it is still possible to die in this fight by losing all of your health before entering what is considered critical health. Sparing her repeatedly will result in her using her weak attack (even if the player is not in critical health) just before she stops attacking entirely.

The Protagonist
Toriel genuinely cares for humans who fall into the Ruins, and the player character is no exception. Toriel is very protective of the player. As the other humans who left her care were killed by Asgore, Toriel tries to keep the player in the Ruins.

If the player kills her during a Genocide run or attacks her when she's showing mercy, she will mock the player and tell them exactly how evil they are. In her final moments she comes to hate the player and regrets letting you pass her.

If the player kills her during a Neutral run she will use the last of her strength to give the player a warning about what lies ahead. Although the player is responsible for her death she will show no contempt and maintains her motherly attitude before she dies.

If you spare her she lets you leave the ruins, but not before giving the player a parting hug.

Calling Toriel on her phone in the ruins and flirting with her makes her assume you're joking, if you do it again she says she's not sure if your interest in her is endearing or pathetic. If you flirt with her after referring to her as "Mother" she will become uncomfortable. She says that the player is an "interesting" child in quotes, implying that she finds the player to be somewhat creepy now.

Choosing to call Toriel only "Mother" will surprise her, and states that if it makes you happy, then she heartily approves of you calling her 'mother'.

Asgore
Asgore is Toriel's ex-husband. Of the two, Toriel was considered to be the more intelligent. They were once extremely close, winning first place in the '98 Nose Nuzzle competition and being openly affectionate to the point where Gerson described them as "insufferable". She is the source of his nickname, "King Fluffybuns".

Toriel left him after the death of their son Asriel and the first Fallen Child because she disapproved of Asgore's plan to use human Souls to break the barrier and restart the war between humans and monsters - and even more than that, his unwillingness to truly dedicate himself to this plan. Because of this and Asriel's death, Toriel no longer uses the Dreemurr family name.

However, it is noted that she still holds him in her heart, as evidenced by having his favourite flower in her room, still baking his favourite pie, and having 3 chairs at the dining table instead of 2, and having 3 rooms in the ruins instead of 2. The bookshelf even has a monster history book mentioning him.

She still appears relatively hostile to him before and after the final battle but it is ambiguous whether they get back together or not in the pacifist ending.

Flowey
Toriel does not seem to know Flowey very well, but doesn't have a terribly high opinion of him after catching him attempting to kill the player and knocking him away with a fireball. Flowey calls her an 'old hag'.

In reality, Flowey is Toriel's son, Asriel Dreemurr, having died and brought back to life as the psychopathic flower known today. Asriel later confers to Frisk that she and Asgore would be better off not knowing the truth about him.

Sans
Although the two didn't know each other's names until the end of the pacifist route, prior to the events in Undertale, they told jokes to each other through the door leading to The Ruins.

At one point, Toriel requested that if a human were to ever come through the door, he'd keep them safe. Even though Sans hates making promises, he agreed to keep it.

They bond after the final boss fight in the pacifist run, texting Frisk multiple times as they walk through the Underground.

Trivia

 * If the player kills Toriel, the next time they go to fight Toriel (after loading or restarting the game), before the fight, she will say, "... wait. ... why are you looking at me like that? Like you've seen a ghost. Do you know something that I do not? No... that is impossible." Additionally, during the battle, if you attempt to talk to her, the text box will say, "You thought about telling Toriel you saw her dead. But.. that's creepy."
 * After you've chosen the pie flavor in the Toriel's call in the Ruins and you reset the game and she calls about the pie again, Toriel recognizes the player's choice and asks to confirm. Toriel will say that you remind her of someone, saying "It's like meeting an old friend for the first time."
 * Her physical aesthetics appear similar to that of Falkor the Luck Dragon, from the fantasy movie The Neverending Story. Her appearance is also very similar to that of a Mimiga, a creature from the game Cave Story.
 * Toriel's name appears to be a pun on tutorial, as she teaches the player about how the game works.
 * If you type "Toriel" for the character's name, the response becomes "I think you should think of your own name, my child" and prevents you from using the name.
 * When Gerson is asked about Asgore, he reveals that Toriel once wore a flower patterned muu-muu, which led other monsters to compliment her by saying "nice muu-muu". Toriel assumed everyone was calling her a cow, so she never wore it again.
 * If you end the battle with the dummy by boring it, Toriel will stare in confusion before moving on as if the fight never happened.
 * If you return to the house after sparing her, you will find she is missing. You can find her at the flower bed that you spawn on at the beginning of the game.
 * Toriel's name sounds similar to the Spanish word "toro", meaning bull. This could be a reference to the above "nice muu-muu" compliment or her bull-like appearance.
 * If you decide to call Toriel on your Cell Phone right before you exit the Underground in the True Pacifist Route you will get text messages from her and occasionally Sans will drop in and send some texts as well.
 * If you kill Toriel and then try calling her afterward, it will say "Dialing..." and then ends the call with "But nobody came."
 * Toby Fox has confirmed that it's possible for Toriel to have said the word "Fuck".
 * Toriel is based on Toby Fox's mother.