Threshers are blue Metal element Slugs. It is the favourite Slug of Sergent Slug, the owner of Club Slug. When they transform after hitting 100 MPH, they gain characteristics of both a tiger and a shark. The thresher slug is named after the Thresher shark famous for its bony tail.
- A famous Thresher is Buzzsaw, who belongs to Eli Shane.
- A famous Thresher is Butch, who belongs to Sergent Slug.
- A ghouled Thresher is called a Thrasher.
A Megamorph Thresher is first seen in an official art in Slugterra: Return of the Elementals, while its official appearance is first seen in the Slugisode Trick or Cheat! and Slugterra: Into the Shadows.
- Protoform Abilities - Can chomp through things.
- Sawtusk - Huge chomping bite.
- Throttlebite - Curls into a flat circle and spins like a saw blade, boney spines on the outside to slice things.
- Trillioblade - Flings saw blades from its tail.
- Blasterblash - Chomps on to an opponent's blaster then spins like a sawblade, sawing it in half.
- Magma Saw: "Thresher"+"Forgesmelter" - Forms a superheated spinning magma sawblade that spews lava from its sides and can easily melt and cut through most metals.
- Slicing Rope: "Thresher"+"Polero" - The Polero grabs the Thresher, spinning it at high speeds, leading to a bolo-like appearance.
- Toxic Tusk: "Neotox"+"Thresher" - TBD. It hasn't officially appeared in show yet.
- The World Beneath Our Feet Part 1 (First appearance)
- The World Beneath Our Feet Part 2
- The Trade
- Club Slug
- The Slug Run
- Endangered Species
- The New Kid Part 1
- The New Kid Part 2
- The Journey Home
- The Gentleman and the Thief
- The Hard Part
- The Return
- Mission: Improbable
- Keys to the Kingdom
- The Thrill of the Game
- Back to Blakk (Appears in flashback(s))
- Bandoleer of Brothers
- Light as Day
- Slugterra: Ghoul from Beyond
- Slugterra: Return of the Elementals
- The Fall of the Eastern Champion (Appears in flashback(s))
- The Lady and the Sword
- Slugterra: Into the Shadows