Hotland

The fourth region encountered in Undertale, Hotland proceeds Waterfall and precedes the Core. It is the home for the Lab, as well as many of the game shows of Mettaton. Between Hotland and the Core the MTT Resort can also be found.

Appearance
The Hotland is an arid, region with reddish orange dirt. Many of the puzzles in the area involve platforms, adding to the hot atmosphere, as well as foreshadowing the technology found in the Core. The area also introduces the orange bullet mechanic by way of orange security lasers.

Pacifist Route
After defeating Undyne, the player makes their way to the Hotland. Three paths are available, one leading to the River Person (the first place they are encountered), one to the Lab, and the final route blocked off by 01 and 02, but leading to the Hotland Elevator. After entering the Lab, meeting Alphys, and being confronted by Mettaton for the first time, Alphys upgrades the protagonist's Cell Phone to include two storage boxes, as well as several additional featured used to combat Mettaton in the several following encounters within the Hotland. Included was a jet pack to chase the rising can of MTT-Brand Always-Convenient Human-Soul-Flavor-Substitute in Mettaton's cooking show, a bomb defuser in Mettaton's TV news report, and the Yellow Mode combat feature when Mettaton attacks the player once more. Along the way, the main character must also defeat 01 and 02, as well as solve several steam-based puzzles and shooting mini-games.

After making it to the end of Hotland, the player reaches MTT Resort, where they have a chance to talk to Sans, shop at either Bratty and Catty or the MTT-Brand Burger Emporium, or continue onwards towards the Core.

Enemies

 * Vulkin
 * Tsundereplane
 * Pyrope
 * Muffet
 * Royal Guards

Trivia
For the requirements of the Genocide Route, Hotland and the Core are combined as a single region.