Frightgeists are rare psychic element slugs with cyan skin and white patterns on their body. Their protoform has a skeletal pattern. Its first major appearance is in the episode "Deadweed" and is found in the cavern of the same name. This slug has mostly fear-related moves. They are notable for being the only known Slug who can directly attack a Darkbane.
- Protoform Abilities - Makes you feel creeped out; can be an early warning system of approaching danger.
- Frightningrod - Hits an opponent creating an overwhelming, uncontrollable fright response.
- Slugbane - Creates the illusion of a monstrous slug predator, scaring an opponent's slugs. Panicked ammo is hard to control.
- Mysteria - Ghost mode can penetrate walls.
- Spellaport - Creates portals in the air that can reroute fired slugs and attacks.
- Ectophasm - Ghostly ectoplasm energy used as slashing arms.
- Ghostshroud - Bits of ectoplasm break off and turn into swirling ecto-beings that act as a shield.
- Arachnoshroud: "Arachnet"+"Frightgeist" - TBD. It hasn't officially debuted in the series yet.
Frightgeists are excellent defensive slugs. Its Spellaport move provides slingers an excellent defense against their opponents, and can also be considered an offensive move if slugs are rerouted toward their slinger. It is most well known for its Frightningrod move, an effective attack that terrifies even the toughest slingers, and its Slugbane move, which scares Slugs. This can be a useful defensive attack against experienced slingers, as it takes away their options.
- Club Slug (First appearance)
- Shadows and Light
- Bandoleer of Brothers
- Light as Day
- The Fall of the Eastern Champion (Appears in flashback(s))
- In the episode "Club Slug", Kord is holding a Frightgeist.
- The Frightgeist's Megamorph Protoform is first seen in Slugterra: Slug It Out 2.