The beast appears to be a octopus-like creature. It is very large, and emits a red glow from its eyes. Its body is largely transparent, being largely non-corporeal, but it also possesses spots of orange bioluminescence. The more it feeds the more solid it becomes.
It first appears in "It Comes by Night", terrorizing an unnamed cavern. After attacking a number of owned Slugs, Brodie contacts the Shane Gang hoping Eli would use his healer slug to help restore the Slugs' drained energy. Eventually the cavern's town council decides to put a bounty on the creature's head. This draws "Fire & Ice", the Power Triplets and Gerhard Stocker into the fray. After a heavy battle in the forest, the creature flees. Later the cavern residents prepare to fight back with its only weakness: Phosphoro Slugs. This is when Eli Shane lures it into absorbing more slugs, causing it to become solid. Eventually it is brought down by Eli and Gerhard, causing it to release all the energy it previously absorbed. In "Light as Day", it was seen coming out of Dr. Blakk's terraportal and then fighting the Shadow Clan. And it was succeeding until Doc saved the day. In "Return of the Elementals" they helped the Darkbane get to Upright Cavern so they could Ghoul the Fire Elemental.
- Spirit Syphon - The beast is able to drain the spiritual energy of slugs and people with it's tentacles.
- Intangibility - It can change its molecular density (it can hit you, but you can't hit it), however if it absorbs to much energy, it won't be able to use this ability and thus will remain solid.
- It's ability to drain ones spiritual energy may be based on the chupacabra, a creature allegedly living in Latin America that is said to be able to completely drain the ones blood.
- In Return of the Elementals, Eli Shane refers to these creatures as Eels.
- Eels see anything that they can drain the energy of, like slugs or people, in bright orange.
- When they die, they release the spirit's of things they have drained.
- Highly non-canonical to the show, the infamous "High Plains Monster" makes an extremely rare return in game form in Slugterra: Slug It Out 2 as an exclusive one-time rare boss battle in story mode.
- Unlike the show where the "High Plains Monster" is seen as a transparent thing to a later dark brownish-blue creature and wreaking havoc in High Plains Cavern, which it's named after, in the game the creature appears as pale milky-white creature in The Dark Periphery.
- Also it can project purple waves that disrupt the brain. It can also summon purple monsters that catch slugs that are flying towards them and take them back to the slugslingers.