Undertale is a role-playing video game created by American indie developer Toby Fox. The player controls a child who has fallen into the Underground: a large, secluded region under the surface of the Earth, separated by a magic barrier. The player meets various monsters during the journey back to the surface. Some monsters might engage the player in a fight. The combat system involves the player navigating through mini-bullet hell attacks by the opponent. They can opt to pacify or subdue monsters in order to spare them instead of killing them. These choices affect the game, with the dialogue, characters, and story changing based on outcomes.
Fox developed the entirety of the game independently, including writing and composing the score. Additional art was created by other artists, primarily Temmie Chang. The game took inspiration from several sources. These include the Mother and Mario & Luigi role-playing series, the bullet hell shooter series Touhou Project, and the British comedy show Mr. Bean. Originally, Undertale was meant to be two hours in length and was set to be released in mid-2014. However, development was delayed over the next three years.
The game was released for Microsoft Windows and OS X in September 2015. It was also ported to Linux in July 2016, PlayStation 4 and PlayStation Vita in August 2017 and the Nintendo Switch in September 2018. The game was acclaimed for its thematic material, intuitive combat system, musical score, originality, story, dialogue, and characters. The game sold over one million copies and was nominated for multiple accolades and awards. Several gaming publications and conventions listed Undertale as Game of the Year. The first chapter of a related game, Deltarune, was released on October 31, 2018.
Undertale is a role-playing game that uses a top-down perspective. In the game, players control a child and complete objectives in order to progress through the story. Players explore an underground world filled with towns and caves, and are required to solve numerous puzzles on their journey. The underground world is the home of monsters, many of whom challenge the player in combat; players decide whether to kill, flee, or befriend them. Choices made by the player radically affect the plot and general progression of the game, with the player's morality acting as the cornerstone for the game's development.
When players encounter enemies in either scripted events or random encounters, they enter a battle mode. During battles, players control a small heart which represents their soul, and must avoid attacks unleashed by the opposing monster similar to a bullet hell shooter. As the game progresses, new elements are introduced, such as colored obstacles, and boss battles which change the way players control the heart. Players may choose to attack the enemy, which involves timed button presses. Killing enemies will cause the player to earn EXP (in turn increasing their LOVE) and gold. They can use the ACT option to perform various actions, which vary depending on the enemy. If the player uses the right actions to respond to the enemy, or attacks them until they have low HP (but still alive) they can choose to spare them and end the fight without killing them. For some boss encounters to be completed peacefully, the player is required to survive until the character they are facing has finished their dialogue. The game features multiple story branches and endings depending on whether players choose to kill or spare their enemies; and as such, it is possible to clear the game without killing a single enemy.
Monsters will talk to the player during the battle, and the game will tell the players what the monster's feelings and actions are. Enemy attacks change based on how players interact with them: should players choose non-violent options, enemy attacks are easy, whereas they become difficult if players choose violent options. The game relies on a number of metafictional elements in both its gameplay and story. When players participate in a boss battle on a second playthrough, the dialogue will be altered depending on actions in previous playthroughs.Undertale takes place in the Underground, a realm where monsters, once equal to humans, were banished to after war broke out between them. The Underground is sealed from the surface world by an imperfect magic barrier, the only point of entry being at Mount Ebott. A human child falls into the Underground and encounters Flowey, a sentient flower who teaches them the game's mechanics and encourages them to raise their "LV", or "LOVE", by gaining "EXP" through killing monsters.[a] When Flowey attempts to murder the human to take their soul for himself, the human is rescued by Toriel, a motherly goat-like monster, who teaches the human to solve puzzles and survive conflict in the Underground without killing. She intends to adopt the human, wanting to protect them from Asgore Dreemurr, the king of the Underground.
The human eventually leaves Toriel to search for Asgore's castle, which contains the barrier leading to the surface world. Along the way, the human encounters several monsters, including: the skeletons Sans and Papyrus, two brothers who act as sentries for the Underground; Undyne, the head of the royal guard; Alphys, the kingdom's royal scientist; and Mettaton, a robotic television host Alphys created. Some of them are fought, with the human having to choose whether to kill them or to show mercy; should the human spare them, they may choose to become friends. During their travels, the human learns the cause of the war between humans and monsters. Asriel, the son of Asgore and Toriel, befriended a human child who fell into the Underground and was adopted by Asgore and Toriel. One day, the child was fatally poisoned by some flowers. When Asriel returned their body to the humans, they attacked and killed him, resulting in Asgore declaring war. Asgore now seeks to break the barrier, which requires him to collect seven human souls, of which he has six.
The game's ending depends on how the player resolved encounters with monsters.[b] If the player killed some but not all monsters, the human arrives at Asgore's castle and learns that they also need a monster's soul to cross the barrier, forcing them to fight Asgore. Sans stops the human before their confrontation, revealing that the human's "LOVE" is an acronym for "level of violence" and "EXP" for "execution points." Sans judges the human based on the combined resolution of the encounters. The human fights Asgore, but Flowey interrupts them, killing Asgore and stealing the human souls. With the aid of the rebelling souls, the human defeats Flowey, falls unconscious, and awakens on the human side of the barrier; they receive a phone call from Sans, explaining the state of the Underground after the human's departure.
If the player instead kills no monsters and has completed a previous playthrough of the game, Flowey is revealed to be a reincarnation of Asriel, created as part of Alphys's experiments. Toriel intervenes before the human fights Asgore and is joined by the other monsters the human has befriended. Flowey ambushes the group, using the souls of all the monsters to take an older Asriel's form to fight the human. The human connects with their new friends during the fight, eventually triumphing. Asriel reverts to his child form, destroys the barrier, and expresses his remorse to the others before leaving. The human falls unconscious and is awoken to see their friends surrounding them, with the knowledge of the human's name – Frisk. The monsters reintegrate with the humans on the surface, while Frisk has the option of accepting Toriel as their adoptive mother.
Another ending ensues if the player kills all monsters, in which Frisk becomes influenced by Chara, the fallen human child whose body Asriel attempted to return. When Frisk reaches Asgore's castle, Sans attempts to stop them, but Frisk kills him. Flowey kills Asgore in an attempt to get mercy, but Frisk executes Flowey anyway. The fallen human child assumes control and, with or without the player's consent, destroys the universe. To enable further replays of the game, Frisk must first give their soul to the fallen human child in exchange for restoring the universe, which will permanently alter every subsequent Pacifist run