Mysterious Invaders is the fifteenth Chapter in Kid Icarus: Uprising's story line. Pit and Palutena are introduced to mysterious creatures called the Aurum. The Aurum pose a threat to the planet Earth, so they decide to head to the Aurum base to defeat the new enemies and stop the invasion.
 Air Battle
The Chapter starts out with Palutena showing Pit, from a distance, a group of large floating islands ransacking the Earth. Suddenly enemies approach Pit, which he must defeat. Palutena remarks how unfamiliar she is with the new group of enemies and Pit assumes that it's possibly a new unit of Viridi's Forces of Nature. Viridi immediately replies that the she's not the one responsible for pulling the stunt. Hades jumps into the conversation and also states that he's not involved with the enemies as well. Viridi and Hades armies have been fighting one another and both Gods claimed that they would have finished each other's army if the enemies haven't interrupted them.
Hades asks Palutena, if she has any info regarding the enemies, but she states that she only knows that they aren't from this world. Viridi remarks that they are harvesting the Earth and must be stopped as quickly as possible. Palutena agrees, as well as Hades, although the latter just wants the Earth for himself. Therefore, Palutena's Army, Viridi's Forces of Nature, and Hades Underworld Army agree to form a temporary alliance.
As they approach the floating islands, battling more of the mysterious enemies, Pyrrhon, who claims to be a Sun God, suddenly appears to help fight off the invaders. He reveals that the invaders are known as the Aurum, who are creatures that are "beckoned by destruction and corruption". This led Palutena to believe that it's Viridi and Hades fault, although Viridi defends herself stating that the Aurum are the agressive ones and everyone else are the victims. Pit eventually reaches the Aurum base, leading to the land portion.
 Land Battle
Pit lands in the center of the Aurum islands and his goal is to reach the base of the tower to stop the Aurum invasion. He remarks how the island seems futuristic and very well structured, where Palutena replies that the fleet probably used all of the material they've harvested to created the place. As with the air battle, the majority of enemies Pit faces during the Land Battle are the Aurum Fleet, with the occasional enemies from Viridi's Forces of Nature and Hades Underworld Army. At some point, Pit will have to use an Exo Tank to progress through the stage. Towards the end of the stage, Pit must grind a set of rails leading him to a downward spiral path, and finally leading to the base of the tower. As he is going down this final path, Pit is treated to a large number of the Aurum Fleet, who are trying to prevent Pit from accessing the tower's base. The end of the path holds an elevator, which sends Pit to the Aurum Core.
 Intensity Gates
The Intensity Gate requires an intensity of 6.0. The Exo Tank is required to reach this section. After going through the first track, instead of going straight towards the Mimicutie, turn right to go across another track leading to the Intensity Gate. Inside the gate holds a Treasure Chest, as well as one Aurum enemy, which you can easily bypass.
 Boss Battle
The goal of this battle is for Pit to destroy The Aurum Core which keeps the island afloat. There is a shield that protects different parts of the core, where Pit will have to circle around it in order to get an opening to attack. Throughout the arena, the floors will electrify, as indicated by the floor giving off a purple glow. There are also orbs that emit lasers, which Pit must avoid as well. After dealing damage, the Aurum Core will explode, successfully completing the Chapter.
The Chapter ends with Pyrrhon rescuing Pit from the resulting explosion, although more of the Aurum Fleet appears, continuing on with their invasion.
- This Chapter begins a mini arc centered around the mysterious Aurum Fleet.