Undead creatures are collectively referred to as "ghouls" in most media, though the namesake species exists as seen with Ghost Roaster and Chopscotch. After Kaos's defeat in his lair, three of the Skylanders (Spyro, Gill Grunt, and Trigger Happy) returned to the Ruins with the captive Kaos, and Hugo later banished the evil Portal Master to Earth, where he was shrunk and turned into a toy. However, Master Eon hinted to the new Portal Master that the journey with their Skylanders was only the beginning. The name of his secondary ability "Flight of the Wasp", is perhaps a reference to the orchestral interlude, Flight of the Bumblebee. Swarm is voiced by Danny Jacobs, best known for voicing Victor Zsasz in Batman: Arkham Asylum and being the second voice of King Julien XIII in the Madagascar series.

Shortly after the Core's destruction, the Skylanders who guarded it were banished from Skylands to Earth, where they were turned into toys as a result of Earth bearing no magic, and waited for a new Portal Master to find them. Although Master Eon survived the destruction of the Core of Light, he became a spirit and was unable to fight Kaos and The Darkness, leaving the duty of leading the Skylanders to the new, young Portal Master. After Master Eon recruited the new Portal Master, the Skylanders made their suprising return to Skylands, arriving on the Shattered Island to save its Mabu inhabitants from a freak tornado that was ravaging their village. The heroes then began their quest to save Skylands from Kaos' tyranny with the new Portal Master guiding them. The Flying Eyeball (Eye Brawl's head) does the talking, as he refers to the bouncing eyeballs Eye-Brawl summons from the underworld as his 'little brothers'. He also frequently uses Eye puns in his lines.In Skylanders: Giants and Skylanders: Trap Team, the music from Cadaverous Crypt plays in the Undead elemental zones. Skylanders: Swap Force remixes Creepy Citadel's theme instead, whereas the Undead Vehicle Zone in Skylanders: SuperChargers borrows Rampant Ruins's theme. In Skylanders: Lost Islands, the Flying Eyeball mentions that eating a lot of carrots makes him able to see far and well in the darkness in places like the Necropolis. Isle of Man, Isle of Wight, Northern Ireland and the Scottish Highlands) may take longer to reach you. This was the only element in Skylanders: Giants where none of its Skylanders received in-game variants. In Skylanders: Battlecast, he is able to grow roots to restore his own health while increasing his maximum amount, being a formidable tank. His Special Ability is Overgrowth, increasing his max health, and his signature Gear is the Thorncaster, randomly increasing the cost of enemy spells. His scrapped card and signature Relic is the Deepwood Well, which gives power to the active character when they heal.

There is a glitch where if Swarm enters a cutscene or is otherwise interrupted whilst flying, he will land although still be showing the animation of his wings buzzing. In Skylanders: Swap Force and onward, Toys for Bob and Vicarious Visions used generic names for all the new Skylanders before the final names were decided upon. [3] In newer games, some Skylanders keep these placeholder names in the in-game files even after their debut, though most are eventually updated. Eye-Brawl's Soul Gem name is the famous quote from the movie, A Christmas Story, "You'll Shoot Your Eye Out!"In Skylanders: Trap Team 's turret challenges, Undead Skylanders have the special ability Spectre Swarm, which gradually damages enemies in an area. In Kaos Doom Challenge, they can summon skeletal hands as their towers, which throw flaming skulls at enemies and slam the ground while recharging.