Underworld (Kid Icarus)

"Welcome to MY Underworld, Pitty Pat. You too, pretty Palutena."

- Hades "welcomes" both Pit and Palutena to the Underworld.

The Underworld (冥府界 Meifukai, lit. "Hades World") is a vast and dreaded netherworld that is a natural vertical maze, ultimately opening to the Overworld and a location in the Kid Icarus series. It is a dank, dark world filled with evil monsters. Of course, the twisted creatures that inhabit the Underworld only provided a sympathetic ear and allies to Medusa, who was banished here by Palutena. Staging a coup from here, Medusa started her ultimately successful invasion of Angel Land and installed herself as ruler in the Palace in the Sky. Though it was believed that Medusa was the ruler of the Underworld in the beginning, it is revealed in Kid Icarus: Uprising that Hades himself is the true ruler of this realm.

The Underworld boasts a large number of threats and navigation hazards. Pit can expect to find moving platforms, thorny growths in the walls, and small pools of lava that can inflict major damage quickly. Platforms will typically be small and Pit must be careful to avoid stepping off a platform as he lands (holding up on the control pad allows for more a precise landing). The area also sports ice that Pit can fall through and will cause him to slide from momentum.

The Underworld area "wraps around" from one side to another, though the first and second adventure handle it differently.

Kid Icarus
Having just escaped from his dungeon cell, Pit must evade the monsters here and gain access to the Overworld by defeating Twinbellows in the Fortress. This is a vertical series of stages.

Since this is a up-scrolling stage, Pit will die if he falls below the bottom of the screen. An Angel's Feather can help to avoid this fate, but can be difficult to obtain this early. If Pit moves off one side, he will reappear on the other side; clever use of this ability allows for different tactics when moving and attacking, but it's (almost) never necessary to use this.

Stage 1-1
Here's where Pit's daring escape from the dungeons begin, and it is never an easy trip. Though this area begins with long, flat platforms, it quickly becomes a tricky jumping gauntlet and Pit's foes are uncompromising.

Stage 1-2
The level starts out as the previous level, which long platforms. However, climbing is a bigger focus here. The ice platforms are introduced early here and are located throughout the level.

Stage 1-3
The stage starts similarly to the first one. Lava pits are noticeably present in the level itself (and oddly, harmless candles in the background as well). All of the enemies from the past stage make a return.

Stage 1-4
The fortress level of the Underworld.

Kid Icarus: Of Myths and Monsters
Pit starts through this area on his path to earn the strength to use the Three Sacred Treasures. This area doesn't have a clear "wrap around" border. Pit will smoothly transition horizontally and is indeed necessary for continuing.

Stage 1-1
Pit will encounter only a few basic foes here as he leaves on his journey to become worthy of the Three Sacred Treasures. He'll also get his first taste of platform jumping and avoiding spiky thorns.

Stage 1-2
Pit will get his first encounter with icy platforms in the level of the tower and an increased amount of thorns. The Reaper makes an initial appearance, too.

Stage 1-3
The platforming gets trickier here with many single-block landings. Pit must be careful when navigating around thorns. There's a secret chamber right above the entrance; hitting the wall with hammers will reveal a Hot Springs guarded by Totems. Jumping into the water will instantly vaporize the Totems.

Stage 1-4
The first Fortress consists of 25 rooms, arranged in a heart-like labyrinth. The Minotaur guards the Sacred Casket which holds the sacred treasure here. This Fortress will be an easy jaunt compared to those that Pit will have to travel through later, so he'd do well to learn the ways of the Fortress.

Chapter 9: Medusa's Final Battle
In this chapter, Pit finally ventures into the Underworld after getting the Three Sacred Treasures and the Underworld Key from Thanatos. Using the Three Sacred Treasures, he blows through all waves of enemies as he makes his way to Medusa. During the Air Battle, he and Dark Pit slay the Underworld Gatekeeper, and Pit heads into the Underworld Castle. Pit must first defeat replicas of three previous bosses (Twinbellows, Hewdraw Reborn, and Pandora) before beginning to fight his way through the castle. When he reaches Medusa, Pit takes flight with the Wings of Pegasus and engages her in battle. She transforms into Monsterous Medusa as a last resort to defeat Pit, but Medusa is destroyed nonetheless. The castle falls to pieces, and the credits roll as Pit and Palutena begin to celebrate. However, their victory is interrupted when Hades appears and reveals himself as the true leader of the Underworld Army.

Chapter 22: Scorched Feathers
After Pit's wings are burned trying to save Dark Pit, Dark Pit ventures to the City of Souls to find the Rewind Spring. Upon entering the city, he encounters Hades, who sends his Underworld troops at him again. After getting far enough into the city, Dark Pit encounters the Soul-Eating Monster, and destroys it with little trouble. Palutena, Viridi, and Dark Pit then discover that Hades is using souls to create more monsters for his Underworld Army, and Hades exclaims they will never stop him. Eventually, Dark Pit arrives at the Rewind Spring, which can restore anything to its previous state. However, as Dark Pit lands, Pandora jumps out of his body and uses the spring to revive herself. After a short battle with Dark Pit, Pandora jumps in again and reverts into her Amazon form. Pandora does another battle with Dark Pit, but is destroyed by him. Dark Pit then dips Pit's wings into the spring, and Pit is revived.

Trivia

 * The rock formation on a gorge underneath and outside the Underworld Castle, resembles the face of the Underworld's supreme, true ruler, Hades himself.