The Goon is a special megamorphed Goon Doc ghoul that can do more than just corrupt slugs and make people ill. He is the main antagonist of Ghoul from Beyond and Return of the Elementals and the mentioned antagonist of the third season.
The Goon is an especially evil Goon Doc ghoul, seething with dark energy. When it attacks, the Goon has an eerie way of getting into a target Slugslinger’s head. But its thirst for control doesn’t stop there—the Goon is determined to conquer every cavern in Slugterra!
The Goon appears for the first time in "Ghoul from Beyond", with a possessed Junjie and some marauders who find their way into The 99 Caverns from an isolated world located to the East, stealing Fandangos to power their terraportal to allow for more of his armies to gain entry and conquer Eli's world. But while the Shane Gang does manage foil his plans, the Goon however manages to escape and prepare his revenge.
He returns in "Return of the Elementals", possessing Will Shane, and working with a mutated Dr. Blakk & the Darkbane, attempting to ghoul the ancient Elemental Slugs to destroy Eli's beloved world, but with rising tensions between the Goon & Blakk, the Shane Gang manage to outsmart them and free Will Shane from his corruption and with Will's help & self-sacrifice and the evil is sent back into The Deep Caverns.
In "The Fall of the Eastern Champion", it's revealed the Goon was once a Guardian Slug protecting a slug gate in the East, but with the darkness beneath them growing in power, a sinister being known as "The Emperor", who was imprisoned long ago, would be freed and he would ghoul any of the fleeing Guardians he got his hands on, one of which would be "The Goon".
- Ghoul from Beyond (First appearance)
- Return of the Elementals
- Slugterra: Eastern Caverns (Appears in flashback(s))
- Second Chances (Cameo)
- The Fall of the Eastern Champion (Appears in flashback(s))
Moves he has been seen using.
- Protoform Abilities
- Makes people feel ill when standing nearby.
- Emits dark light/energy that allows him to takeover a person's mind & body quicker, and gives them a zombie-like appearance until they're no longer needed. (Darkcloaking without the slinging).
- Can sense the ghouling process from great distances.
- Can read minds without the need to touch or control someone.
- Ghoulgoyle - Hits an opposing slug and uses Dark Energy to transform them into a ghoul.
- Darkcloak (unofficial name) - Hits an opposing slinger and drops them into a temporary coma, while it uses its Dark Energy to takeover their mind & body for its own purposes, and gives the person a zombie-like appearance until they're no longer needed. (This move is a combination of Creepsleep, Ghoulgoyle and Turncloak combined... see Goon Doc).
- The Dark Slinger (Formerly)
- Dark Servants
- The Marauders
- The Emperor
- Shadow Clan (Formerly)
- Dr. Blakk
- Eli Shane
- Kord Zane
- Will Shane
- Shadow Clan (presumably)
- Doc, "The Healer"
- It's unknown if all Goon Docs can do Darkcloaking and sense the ghouling process.
- In Return of the Elementals he is seen working with the Darkbane and Dr. Blakk, plus hosting Will Shane, but it is unknown how he reached the Deep Caverns to ever get to them as the only slug shown to be able to punch a hole to the Deep Caverns is a Tempesto and the Ghouled Air Elemental.
- He is afraid of Doc due to Doc being able to cure ghouls.
- In The Fall of the Eastern Champion, it's revealed the Goon was once a Guardian Slug and was specially trained & tended to by the Shadow Clan and had been guarding at an Eastern Guardian Gate for over 2000 years until The Emperor broke free and corrupted him with his Dark powers.
- He used to be a Guardian Slug before the Emperor ghouled him, however oddly enough it was revealed in Return of the Elementals that he won't transform into a regular Boon Doc. He will turn into a wrinkled up weakened state, and would eventually die, and the only way to cure him is more ghoul energy. A possible reason is that The Emperor ghouled it with so much Dark Energy that Doc isn't able to cure him (like he couldn't cure Dark Water without Fandangos).
- In Return of the Elementals The Goon is revealed to be a mind reader who was able to read the mind of Red Hook without controling him to find any information or the location of the Energy Elemental but found nothing of use.