Phosphoros are blue common light element Slugs. When they reach 100 mph they turns into creature whose appearance is similar to that of an angler fish. The Phosphoros power type is light. In protoform, this Slug can illuminate itself. This abilitiy is shown being used before they sleep, revealing that the light the Phosphoro produces comes from inside its body, as seen by the glowing inside of its mouth, rather than originating on the surface of its skin.
- Protoform Abilities - Flashlight/lantern.
- Arcalyte - Explodes in mid-air in a shower of sparks.
- Flashbang - Blinding flash of light to stun and temporarily blind an opponent.
- Beamblaze - Focuses several beams into one concentrated blinding beam blast.
- Blazerain - A 'hail' of short beam bursts.
- Supernova: "Phosphoro"+"Infurnus" - The slugs spin, while the Phosphoro starts lighting up, the Infurnus boosts the light.
- The World Beneath Our Feet Part 1 (First appearance)
- The World Beneath Our Feet Part 2
- A Distant Shore
- The Journey Home
- The Gentleman and the Thief
- The Hard Part
- The Return
- King of Sling
- It Comes by Night
- Light as Day
- Slugterra: Return of the Elementals
- Slugterra: Eastern Caverns
- Second Chances
- Slug Day
- The Return of the Eastern Champion
- The Phosphoros played a large role in "It Comes by Night" when they were used to corral the High Plains Monster, a creature with a weakness to light.
- Phosphoros debuts as a MegaMorph slug in Slugisode: Bee Cool, Dude.