CORE

For the track with the same name, see CORE (soundtrack).

The CORE (JP: コア) is a sub-section of Hotland, accessible from the MTT Resort. It is a technologically advanced facility that provides magical electricity to the underground. There is an elevator to New Home in the center of the CORE. The entire structure is designed so that the rooms inside can change positions and the layout can be altered.

Features

• Alphys directs the protagonist throughout the area, the former slowly showing more and more sentimentality about her time together with the latter.
• Various CORE-exclusive monsters appearing to be "black sausages" encounter the protagonist, all in fixed locations and orders.
• The protagonist can witness the ice thrown by Ice Wolf melting in the CORE.
• The protagonist fights Mettaton in a dark room, the latter broadcasting the action to his audience and presenting the battle as the grand finale.

Map

Loading scripts

Main story

History

Prior to the events of Undertale, the CORE was built by the former royal scientist, W.D. Gaster.

Neutral Route

Two black sausage NPCs at the entrance to the CORE.

After leaving the MTT Resort, the protagonist enters the CORE, and Alphys immediately becomes worried. There is an excess of enemies, the elevator is not functioning, and multiple pathways have been altered, contrary to the map Alphys claims to have. Alphys attempts to guide the protagonist through the CORE, but she eventually stops talking to the protagonist out of embarrassment.

As the protagonist arrives at the end of the CORE, they meet Mettaton once more. He reveals that it was he who hired monsters to attack the protagonist, broke the elevator, and rearranged the pathways in the CORE.

Mettaton explains that all of the encounters between him and the protagonist, as well as all of the puzzles the protagonist had to complete, were designed by Alphys as a way for her to insert herself into the protagonist's story due to her admiration. Mettaton, however, got bored of the arrangement and began to legitimately plot against the protagonist by the time they entered the CORE. He further explains that gaining the protagonist's SOUL would allow him to prevent Asgore from destroying humanity, as well as cross the barrier and become a star on the surface.

After the protagonist defeats Mettaton, Alphys makes her way into the room and panics over the damage done to Mettaton. While traveling to the elevator, Alphys warns the protagonist that they will have to kill Asgore if they want to return home. The protagonist enters the elevator and leaves for New Home.

True Pacifist Route

Monster encounters in this area stop after receiving (or after receiving the call to obtain) Undyne's Letter. NPCs that take the form of "black sausages" appear and reveal that Mettaton hired them to kill the protagonist, but quit since he never paid them. They also reveal that the CORE was rearranged in anticipation for the protagonist's arrival.

Genocide Route

After leaving the MTT Resort, the protagonist enters the CORE. The elevator is functional, and the door leading to New Home is unlocked, allowing the protagonist to continue straight on to Mettaton.

Mettaton makes his last stand, transforming into Mettaton NEO, but does not attack. The protagonist kills Mettaton in a single attack.

Geography

View of the CORE in Hotland

The CORE is an entirely mechanical complex that is largely blue and cyan with red accents. Purple paths and bridges link some rooms. The CORE appears to be the most industrial and modern region of the underground.

The CORE has lavish decoration. Multicolored neon tubes serve as wall ornaments and embellishments. The floors of many rooms are engraved with intricate patterns. Lasers, both decorative and functional, dot the region. Despite the detail work, some parts of some walls and floors are chipped away.

Ozone, a byproduct of electrical power, is omnipresent below the floor level of the CORE. This explains why the CORE seems to be made of stainless steel, titanium, or platinum; ozone is highly corrosive to most organic materials.

The substance below the ozone quickly melts the ice thrown by the Ice Wolf. The ice supposedly cools the CORE down. However, the lack of cooling may not have immediate effects as the Ice Wolf does not throw ice after Snowdin's evacuation in the Genocide Route. Alternatively, the CORE could be a source of ozonated water, which cleans clothes, sanitizes food, and purifies drinking water. In this case, the CORE not being cooled is not hazardous; ozone simply decomposes into oxygen at high concentrations and temperatures.

The majority of enemies in the CORE are harder counterparts of enemies in the Ruins, some of which also appear in Hard Mode.

Sublocations

CORE approach

The entrance to the CORE is a vertical room with the color scheme of the MTT Resort gradually fading into the color scheme of the CORE. Here, the protagonist witnesses two "black sausage" NPCs backing into the CORE. A surprised Alphys calls the protagonist and informs them that monsters are not normally supposed to be in the CORE.

Lobby

Main lobby of the CORE

The protagonist continues into the lobby, which has an elevator to the north and two northern paths to the left and right. Alphys directs the protagonist to the elevator, which is disabled. She then directs the protagonist to the path on the right, then to the path on the left. The elevator in the lobby reactivates once the protagonist reaches the elevator on the other side.

Fire pit

The path to the right of the lobby leads to a small, square room with a fire pit to the north that is inaccessible to the protagonist. After receiving Undyne's Letter, a "black sausage" NPC appears in this room, admiring the fire pit.

Doorway

Going through the left path of the lobby leads to a rectangular room with a doorway at the end. When traveling through this room, a monster appears and attacks the protagonist.

Laser ambush

Continuing forward, the protagonist enters a room with a bridge that is cut off by a force field. Activating the switch near the force field deactivates it, but it also sends a group of lasers in a specific order. Alphys tells the protagonist that the order is "orange, orange, blue", but once the switch is activated, the order that the lasers come in is inverted (blue, blue, orange). Alphys blames herself for messing up and directs the protagonist forward.

Crossroads

The protagonist continues into a crossroads with a path to the north and a path to the east. Alphys directs the protagonist to the east, but changes her mind and tells the protagonist to go north. The northern path leads to a square room that contains another monster that attacks the protagonist.

Laser bridge

The eastern room contains a bridge with many blue and orange lasers followed by a massive wall of blue lasers. Since Alphys is unable to turn off the lasers, she decides to cut the power for the entire room. When that happens, the way back is blocked by a "battery powered" force field. When the protagonist walks into the wall of blue lasers, the power suddenly turns back on, forcing the protagonist to stop. Alphys is unable to keep the power off, so she instructs the protagonist to move, then stop when the power turns back on. After crossing the bridge, the protagonist continues into the "Core Branch".

CORE Branch

The "Core Branch" is a four-way intersection with a SAVE Point in the middle. The signs in the room inform the protagonist that the northern path and the western path lead to the "warrior's path" and the "sage's path" respectively, and the east leads to "The End". Alphys calls the protagonist, completely at a loss for how to guide them, and eventually stops talking to them out of embarrassment.

The "Core Branch" is split into three sections, leading to different sections.

Western section

The puzzle in the sage's path

Starting from the western path of the "Core Branch", the protagonist enters a room that veers upwards. Here, the protagonist can witness the ice thrown by Ice Wolf travel across a conveyor belt and melt into the ozone pit. Continuing north, the protagonist comes across a vertical room with a western path leading to the sage's path, which is a shooting puzzle similar to the ones in Hotland's Reactivated Door Puzzles. Solving this puzzle unlocks the path to "The End". The northern path leads to a crossroads with an eastern path and a northern path. The northern path leads to a room with a trash can containing a Glamburger, while the eastern path leads to the middle portion of the "Core Branch".

Middle section

Starting from the middle path of the "Core Branch", the protagonist enters a vertical room with an eastern path leading to the eastern portion of the "Core Branch". There is a sign on the path that tells the protagonist to "get lost... And stay that way." Continuing north, the protagonist encounters a four-way crossroads with the eastern and western paths leading to their respective portions of the "Core Branch" and a northern path that leads to the warrior's path. The warrior's path is a horizontal bridge in which three monster encounters take place leading up to a switch at the end of the room. Activating the switch unlocks the path to "The End".

Eastern section

Starting from the eastern path of the "Core Branch", the protagonist enters a room that mirrors the room in the western portion of the "Core Branch", except without the ice. Continuing north, the protagonist comes across a four-way crossroads. If neither the warrior's path nor the sage's path are completed, the eastern path is blocked by a force field that eventually disappears after waiting long enough (hinted by the sign next to it). The western path leads to the middle portion of the "Core Branch", and the northern path leads to another crossroads, again mirroring the room in the western portion of the "Core Branch". The northern room contains a trash can with 100G inside.

Core End

The end of the CORE

After unlocking the way to "The End", the protagonist enters a horizontal room with a bridge and then enters the "Core End", which contains a SAVE Point, a doorway, and an elevator leading back to the lobby.

Mettaton

The doorway leads to a dark room with Mettaton in the center. After Mettaton locks the door, the room suddenly rockets upwards, and the battle against Mettaton begins. After fighting and defeating Mettaton, his deactivated body/corpse is left behind, and Alphys unlocks the door and evaluates the situation.

Hallway

The protagonist continues into a horizontal hallway with an elevator at the end. Alphys follows closely behind, blocking the way back as they travel the hallway. When the protagonist opens the elevator, Alphys stops them and warns them about having to kill Asgore. After she leaves, the protagonist proceeds into the elevator to reach New Home.

Trivia

• Even though the CORE is technically part of Hotland, Mettaton is the only monster who can be encountered in both the CORE and other parts of Hotland.
• The visual design of the CORE, as well as the fact its music continues through battles, was likely inspired by the Ocean Palace in Chrono Trigger, one of Undertale's major inspirations.
• The "smell of ozone" SAVE Point may be a reference to the VVVVVV room captioned "I Smell Ozone".
• Since the CORE is the only non-Hard Mode place to have Astigmatism, Whimsalot, and Final Froggit, and Reaper Bird is composed out of these three enemies, it is possible that Reaper Bird's home is set at the CORE.