Toriel

Toriel Dreemurr is a fictional character and boss in the role-playing video game "Undertale". A motherly figure created as an embodiment of excessive video game tutorials, she is a member of the monster race with hanging ears, small horns, white fur and a purple robe. Literally "hand-holding" the player through the opening sections of the game, the player must attempt to escape the area, upon which point they fight her. The player can choose to kill her or convince her to stop fighting, having implications on the game at large. 
The character has received attention from critics and fans for her personality as well as the atypical moral choice of her boss battle. A version of the character also appears in "Deltarune".
Characteristics.
"Undertale".
The player meets Toriel shortly after they fall into the Underground, where she is seen as a motherly figure who desires to protect the player from its dangers. She teaches the player the mechanics of the game, encouraging them to show mercy to enemies rather than attack them. Giving the player a phone with which to contact her, she leaves the player on their own to figure out the rest of the Ruins, after which they arrive at her house. 
While she attempts to take care of the player, they become restless and attempt to leave the Ruins. Having seen several human children die at the hands of the monster king Asgore, she fears for the player's safety and confronts them in battle. If the player chooses not to kill her, the battle is "long and arduous" with little indication that the player's tactics are working until she relents. In fact, she must be spared many times in order to persuade her to allow the player to leave the Ruins. If Toriel is killed after she relents, however, she tells the player that she realized she regrets trying to have raised the player.
It is later revealed that Toriel was once Asgore's wife, Toriel Dreemurr, and they had a son, Asriel Dreemurr. When Asriel died, she gave up her crown due to her disagreement with Asgore, over his willingness to kill human children to break the seal holding the monsters underground.
Near the end of the True Pacifist route, Toriel arrives at "New Home" (The Monsters' Capital) and saves the human from Asgore. However, Flowey appears and absorbs her soul along with all the other monsters in the Underground to regain his true form, Asriel. Later, after the player has fought Asriel, and he has broken the barrier, Toriel and the other monsters leave the Underground. Toriel offers to provide a home for the human; the player can choose to accept or reject this. In the non-playable pacifist epilogue we see that Toriel has achieved her dream of founding and teaching a school.
"Deltarune".
In "Deltarune", Toriel is the adoptive mother of Kris and biological mother of Asriel. She wakes up Kris at the beginning of the game and drops them off at school. After returning from the Dark World, Kris receives a call from Toriel, who tells them that they are in trouble for being late. However, she seems pleased to hear that Kris has made a friend, and allows Kris to explore the town before coming home. She later appears when Kris returns home. It is hinted in the game that Toriel works as a teacher for a younger class at Kris' school.
Development.
Toriel was initially envisioned by the game's creator, Toby Fox, as a "tutorial person that can't stand to see you leave". She was later incorporated as the final boss of the game's demo, which was used to promote its successful Kickstarter campaign.
Merchandise.
An official Toriel plush was released by Fangamer. The plush contains a white heart soul inside, which can only be found if the plush is cut apart. This detail reflects her death scene in "Undertale", and was described by Kotaku as "weirdly unsettling". A figure of Toriel was also released by Fangamer as part of a set.
Reception.
Jess Joho of Kill Screen called the character "relying on the inhumanly selfless portrait of motherhood", but doing so with a purpose, praising the boss encounter with her as respecting the player's ability to think through a problem, as well as their basic instincts as a human being. She stated that the game holds up a mirror to "patriarchal" game design that encourages players to impatiently "sacrifice their own mother and humanity" rather than engaging with the enemy on a "human level".
Nathan Grayson of Kotaku stated that while he killed Toriel during his playthrough, his encounter with her made him cry due to her friendliness and relatability as a character. He also praised the game for remembering this on his next playthrough. Jack de Quidt of Rock, Paper, Shotgun called the tutorial sequence featuring her "beautifully paced" and praised the character, saying "Toriel's all right", while Richard Cobbett of the same site called her sprite animations "understated but effective".
Julie Muncy of Kill Screen criticized the encounter with Toriel as unintuitive, saying that she lost the ability to trust the game after being seemingly forced to kill Toriel, which forced her onto the game's "Neutral" route.