The Reset Bomb is a powerful weapon created by Viridi that restores the covered blast radius to its original natural state. They are "grown" rather than manufactured at the Reset Bomb Depot. Viridi claims that they're totally organic. However, Hades challenges this, forcing Viridi to admit that they're "not entirely" organic. They are apparently "grown" within the Reset Bomb Pod, contained in the heart of the depot. Whenever Reset Bomb detonates, it turns the area into a Reset Bomb Forest.
Pit is flying above a war between humans in Chapter 11, Viridi, Goddess of Nature, when a Reset Bomb crashes down onto the human armies. Pit travels inside the forest produced by the Reset Bomb to see what has happened to the humans.
In Chapter 12, Wrath of the Reset Bomb, Pit travels to the Reset Bomb Depot to stop the production of the destructive weapons. Pit succeeds and the depot is destroyed, causing an end to the creation of the bombs, or so was thought.
The Reset Bomb makes its final, unexpected, appearance in Chapter 17, The Aurum Brain, even though the Bomb Depot was destroyed. Viridi hopes to destroy Aurum Pyrrhon with her most powerful attack. Unfortunately, the explosion does nothing, as Pyrrhon uses his new-found strength to incinerate the bomb before it can do any lasting damage.
Bombs used by Viridi to restore the natural order. The explosion of a Reset Bomb triggers a flood of brambles that in turn become a potent fertilizer. The land around the impact soon becomes dense jungle, uninhabitable by humans.
The Reset Bomb can be seen in the 3DS version in the Reset Bomb Forest stage. It makes its appearance in the background after Viridi appears as it can be observed crashing into the earth then detonating, causing the landscape to change into the forest.