Fang of the Dark Lord
Isle at the End of the World
The Fang of the Dark Lord is located on the monster-ridden Isle at the End of the World, in the sea west to the mazoku barrier, on its fringe. The relic is hidden deep within the cavern on the island, from which no one has ever come back alive.
It is initially described as an extremely rare and invaluable jewel, able to yield a handsome price. Huraker directs Lina Inverse to fetch this curio to settle the debts owed to her. In appearance, the Fang of the Dark Lord lives up to its name. It looks like an enormous incisor protruding from the ground, having a glossy and reflective surface, which is almost blade-like.
When Lina stumbles upon it, she deduces that it is far too big to be transported and casts Dug Haut to shatter it into smaller pieces to collect. However, the island soon begins to sink underwater, unleashing watery serpent-like creatures. Lina is eventually sucked into a whirlpool and is left stranded on an unknown land, separated from Gourry.
The origins of the Fang of the Dark Lord remain shrouded in mystery. Its appellation suggests a strong affiliation to the mazoku, and more specifically to Ruby Eye Shabranigdu, although this is left uncertain. Nonetheless, the appearance of watery monsters, the maelstrom's suspicious ability to transport Lina miles away, Gourry's comical sighting of dolphins close-by, and the island's location in the Demon Sea, all seem more than coincidences that seem to insinuate Deep Sea Dolphin's involvement.
Throughout Slayers: Knight of Aqualord, the Fang appears to be an ominous relic that is far more than what it seems. It is only later revealed that the Fang is a powerful conduit of demonic power and that Huraker sought its shards to allow mazoku access into the outside world to secure her schemes.
Imbuing the shard with black magic
The fragment shattering upon successful use.
In close proximity to even fragments of the Fang, mazoku act and move more freely, having been previously weakened by their distance to the mazoku lords. Lesser demons also tend to surface in the near presence of these fragments, though it is probable that a stronger mazoku would have to be around to orchestrate such incidents. Moreover, black magic spells calling upon specific mazoku become castable only by being channeled into one of the Fang's pieces, shattering it in the process; for example the Dragon Slave, a feat normally unfeasible in the world outside the barrier.
In reality, the Kōma War led to the majority of the mazoku being concentrated within the mazoku barrier. The manga, while not venturing into explicit details, suggests that the mazoku lords' fixed range, coupled with untethered shinzoku energies, limits black magic along with the mazoku's overall activities outside of the barrier, especially, for ranks below high-ranking mazoku. This hindrance presents itself through an overall palpable absence of monsters and the mazoku's restricted ability to fully deploy their power on lands far away from the Slayers peninsula. High-ranking mazoku, however, do not seem to be affected by such constraints as they display unrestrained strength.