- “In the Underworld, gruesome ghouls lurk around every corner.”
- —Skylanders Universe: Book of Elements: Life and Undead
The Underworld, also known as Ghost World or the Land of the Undead, is a location of unknown size or region which holds most of the Undead population in Skylands. Set in lower areas than most islands, it is said to be a dark place that would be absolutely terrifying if it wasn't for its delicious pies. Through the Skylanders series, the Underworld has appeared in the form of many levels and has been part of the backstories of many Skylanders. Many monsters and strange creatures lurk in the the Underworld, such as Rhu-Babies, flying eyeballs, and Vampires.
Though details are unclear, three rulers of the Underworld have been mentioned - Philosopher King Mortalannis, said to be the first Lord of the Undead and owner of the Skull Mask, Malefor, self-proclaimed Undead Dragon King, and Count Moneybone. The latter two have an indirect relation that is yet to be explained.
Aside from the dangers that lurk in it, the Underworld also appears to turn any living creature that wanders deep enough into it Undead as well (Hex and Fright Rider being examples), though there are spells to repel it.
The region also appears to have some sort of cosmic barrier as well, permitting access on foot or portals, but more unstable forms of transportation such as Rifts require large amounts of power to pass through.
Skylanders: Spyro's Adventure
Skylanders: Swap Force (3DS Version only)
- The Underworld appears to be based on the concept of afterlife in mythologies such the Greek Underworld - specifically the Asphodel Meadows, where the dead lose their identity from when they were living and no sunlight enters.
- Different parts of the Underworld also appear to take on inspiration of various scary settings in media, such as somber and abandoned dungeons often seen in Tabletop RPGs, haunted castles and Day of the Dead inspired towns.
- Though traveling to the Underworld is usually said to be difficult, Mako in Twisty Tunnels opened holes into it by digging, though possibly because of the high Undead energy in the area.