Chara

"You and I are not the same, are we? This SOUL resonates with a strange feeling. There is a reason you continue to recreate this world. There is a reason you continue to destroy it. You. You are wracked with a perverted sentimentality. I cannot understand these feelings any more. Despite this. I feel obligated to suggest. Should you choose to create this world once more. Another path would be better suited."

- Chara if the player chooses to do a second No Mercy route "A cotton heart and a button eye / You are the apple of my eye"

- Chara upon CHECKing the dummy. Chara (last name Dreemurr upon being adopted by Asgore and Toriel) also known as the Fallen Human or First Human, is a posthumous character and a hidden protagonist in the 2015 videogame, Undertale, enabling the protagonist, Frisk, to save the game's main antagonist and guiding them throughout the Underground. They serve as the narrator throughout every route of the game, helping Frisk and the player whether they choose to show mercy to the enemies encountered throughout it or to slaughter them all and erase the world.

Chara, at full LOVE, is the only being in Undertale capable of directly challenging the player's influence over the world. However, they are still powerless against the player's indirect attempts (editing the game files) at controlling the world.

Backstory
For reasons they never disclosed even to their closest friend Asriel, but which are highly implied to be abuse of some sort, Chara despised humanity and its actions, despite being human themself. This seems to have driven them to climb the mountain which no one returns from in what was likely an attempt at suicide. Coming across the cave that led to the Underground, they tripped on a root and tumbled into the hole where the monsters lived their lives after the war against humans.

A young Boss Monster by the name of Asriel Dreemurr befriended Chara, and his mother and father Toriel and Asgore took Chara in and raised them as a second child and beloved sibling to Asriel.

A notable event during Chara’s stay with the Dreemurrs was when they attempted to bake a pie with Asriel for their adoptive father, King Asgore. As children are wont to do, they mixed up “buttercups” and “cups of butter” and accidentally poisoned Asgore.

Although they were said by Asriel to “laugh it off”, it was clearly a heavy weight on their conscience, for they later decided to take their own life in the same, horrific way. Their plan was to give Asriel their soul, thereby allowing him to pass through the Barrier that trapped monsters underground and take six human souls from the surface. These he could then use to break the Barrier entirely and free his people. The fact that they woke up after all and shared equal control of the body with Asriel would have come as a great surprise. But, just as they had promised Asriel, they attempted to carry out their plan together.

Upon reaching the village where Chara had grown up, Asriel was unable to bring himself to kill any of the humans. Due to his horrific appearance they attacked him, but he was paralyzed as Chara wanted to fight back to protect him, though he did not. He was struck with blow after blow until Chara gave up. He picked up Chara’s body, which he had brought with him, and returned to the Underground to die before his parents.

Asriel’s remains and memories were placed into one of the golden flowers that grew around his dead body by Alphys’ experiments. The flower was imbued with determination, and Asriel to be reborn as Flowey. Chara's SOUL and consciousness, however, remained dead.

No Mercy Route
In the No Mercy Route, the player corrupts Chara and causes them to become violent, similar to Flowey. As they kill more and more monsters, Chara begins to assume control wherever possible to speed the game up, much like a typical RPG player grinding. Under the player’s guidance, they kill every monster in the game, including Toriel, Papyrus, and Undyne, all of whom try to convince the player to stop.

Upon arrival at Asgore's palace, Sans confronts Frisk, surprisingly and efficiently proving to be possibly the most powerful character in the game. Despite having the weakest of defenses - his HP, ATK and DEF stats being a mere one - he dodges the player's hits, which makes the entire battle a struggle to land a single, fatal blow. The last hit is delivered by the player after Sans falls asleep, which misses, before Chara takes control and manages to strike Sans by surprise. He then reminds the player that he warned them of the consequences before “heading off to Grillby's” and seemingly dying and dissolving off-screen. The player then proceeds to attack Asgore even when he kindly spoke to them - because he failed to recognize Frisk's body as that of a human. Asgore is then killed by a horrified Flowey, who was enthusiastic about the player's choice to destroy the Underground's entire population, but who knows he is going to be killed as well. Flowey claims that he had never betrayed Chara - despite warning Asgore of Frisk's arrival - and begs them to not kill him as he contorts his face to mimic Asriel. Chara gives back control to the player at this point, being hesitant to kill Flowey and giving the player one last chance to back out of the No Mercy Route by closing the game.

If the player continues, Chara completely slashes Flowey out of existence and reveals themself at last, claiming that all the power stats represent themself. They ask the player to join them in destroying the world. At this point, the player can still back out by closing the game, but choosing either option results in Chara destroying the world and closing the game themself in the process.

If the player reopens the game, they will only encounter a void where the Underground once was. After ten minutes, Chara will appear and offer them to return the world in exchange for their soul. To fully restore the world, the player has to accept; otherwise, Chara will leave until the player restarts the game and waits ten more minutes.

If the world is restored and the player completes a True Pacifist Route, its ending is tainted. If Frisk chooses to stay with Toriel, Frisk wakes up with Chara's features and emits a slower version of Flowey's signature laugh. If Frisk claims to have places to go, Chara replaces Frisk in the picture in the end and crosses everyone else's faces out, implying that Chara killed them all.

If the player completes the No Mercy Route a second time, Chara will greet the player again. Chara describes them as "wracked with a perverted sentimentality", stating that not even they could understand doing a second No Mercy Route and instead suggesting the player try the True Pacifist Route. Chara will then make the same offer to destroy the world as they did before, with the same results of the player's choice in both routes.

Neutral and True Pacifist Routes
At any time, should the player fail to meet an area's requirements to continue the No Mercy Route (save Sans, who kills Frisk if they accept his offer when he pretends to spare them), Chara and Frisk have the option to continue without grinding for more EXP and attain one of the neutral endings.

Throughout these routes, just as in No Mercy, Chara provides flavor text for Frisk and the player. However, these routes show a very different side to their personality. Gone are the blunt and harsh fragmented sentences of the No Mercy route. Chara shows themself to be sarcastic, make puns and jokes, and become so overcome with emotion during the fights against their parents that they fall completely silent. They clearly have a large vocabulary for someone so young and enjoy describing the world around them. While somewhat abrasive and suspicious of Frisk at first, they slowly grow more fond of them.

During the True Pacifist final boss fight against Asriel, it is implied that Frisk SAVEs Chara. Through Chara’s memories of Asriel his rampage is finally stopped, and he uses the power of all the souls he has absorbed to break the Barrier and free monsterkind.

Of note is the fact that Flowey, later transformed into Asriel when he regains his original body at the end of the True Pacifist Route, mistakes Frisk for Chara even when they are on the True Pacifist route. When he realizes his mistake, the player learns that the name Chara - or any name they chose at the creation of their save file - isn't the protagonist's, but the first human's. This realization doesn't occur in the Neutral or No Mercy Routes, as Asriel isn’t properly SAVEd and still holds on to the memory of his sibling.

Trivia

 * Chara notes that they were confused at first upon awakening, and the player taught them just how essential power is for success.
 * This means that the true main antagonist (or at least the Bigger Bad) of the No Mercy Route is the player themselves, as they are responsible for Chara's evil and exist outside of their control.
 * Even when Chara removes control from the player by deleting the world, the player can regain control by editing the game files to their will.
 * It is implied that they are the narrator in the Neutral or True Pacifist Route as well, making them a benevolent character who helps guide Frisk through the Underground and that the True Pacifist Route is the path to their redemption for what they wanted to do to humans.
 * Chara has several implicit connections with other characters:
 * They seem to idolize Undyne, referring to her as a hero in all routes.
 * This is particularly notable in the No Mercy Route, where they fall silent as she slowly melts.
 * They share many similarities with Toriel. Both laugh in distress and talk similarly, including saying "Greetings." and using few if any contractions.
 * In one of Asgore's drawers in New Home, a knitted sweater can be found with the words "Mr Dad Guy" on it. On the No Mercy Route, Chara remarks "Still has that sweater", which implies they are the one who knitted it.
 * They know that Asriel's revived form is named "the absolute GOD of Hyperdeath!" and has specially named attacks, implying that this is a character he created and told Chara about.
 * The battles against Toriel, Asriel, and Asgore are the only ones other than Undyne's where Chara will fall completely silent.
 * They make a special note of Snowdrake on the No Mercy route, calling it "That comedian" at Snowdin save points. If the player does not kill Snowdrake, they will remark "The comedian got away. Failure." These lines do refer to Snowdrake, despite the common belief that they refer to Sans.
 * If the player decides to laugh at Snowdrake's mother, Chara is the one that starts laughing while Frisk doesn't, and if the player tries to laugh again, they say that it isn't funny, implying laughing in stressful situations was a coping mechanism while they were alive and before being corrupted by the player.
 * Many details throughout the game imply Chara was abused and self harmed.
 * Toriel's gardening tools are blunted and her fire is not hot enough to burn. She also hides her knives.
 * The flavor text they give for the faded ribbon is "If you're cuter, monsters won't hit you as hard." which carries grave implications.
 * Chara is implied to like chocolate, as their narration when checking Asgore's fridge says "No chocolate".
 * They also read quite a bit, as evidenced by their expansive vocabulary and a word-for-word quotation from Banana Yoshimoto's Kitchen in the No Mercy Route.
 * They seem to enjoy learning in general, such as when they get very excited to learn that Toriel owns a "water sausage", which they did not know the name of until reading it in a book ingame.
 * They are a fan of anime, particularly Mew Mew Kissy Cutie 2, calling the section where Alphys says it's trash the "Bad Opinion Zone".