- Order: Leviathan
- Suborder: Sea Wyvern
- Infraorder: Thunder Shell Wyvern
- Family: Lagiacrus
Abyssal Lagiacrus is a part of the Leviathan class. This Leviathan is rarely seen due to its habit of hunting for prey in the dark depths of the ocean. Its existence has been known for many years but remained impossible to prove as it was only in ancient text. The Abyssal Lagiacrus's true identity is a powerful, 100 year old Lagiacrus, or Ivory Lagiacrus, individual that has gotten bigger over many years and has completely moved to the dark sea.
Abyssal Lagiacrus are known to live in the deep in the darkest part of the seas. The only real possible place to hunt one down is in the Underwater Ruin if one happens to travel in it.
Abyssal Lagiacrus were once top predators in the shores of their previous environments, but now aren't able to easily catch some larger prey due to their new life style. Abyssal Lagiacrus now have specialized in catching deep sea prey like fish and some species of lobsters. Rarely, Abyssal Lagaicrus can catch prey like Epioth. The only known monsters that could potentially be a threat for this monster is an adult Gobul, Ceadeus, the older Goldbeard Ceadeus, and Nakarkos.
An average Abyssal Lagiacrus is approximately 3969.3cm long. The Abyssal Lagiacrus lives in the deep depths of the sea. Though very few Abyssal Lagiacrus have ever been encountered, information gleamed from the Hunter-killed and naturally killed corpses provides some telling information. From living in the dark depths, Abyssal Lagiacrus's scales have become darker in color to fit in with the environment. Though it has become darker in color, some of its scales have an eerie glow to them due to it constantly being charged up with lightning, unlike normal Lagiacrus individuals. Abyssal Lagiacrus are constantly charged up due to a different organ from their Shell Shockers, known as an Dynamo. Very little is known about this organ, though it is being researched by the Hunter's Guild. It is said that this organ turns the sea around it into a electrified weapon. In order to catch prey, it uses its glowing scales as a tool to attract deep-sea prey to its location. This makes catching prey easier for it. Just like its younger kin, Abyssal Lagiacrus use whirlpools to capture and drown prey.
Abyssal Lagaicrus are dangerous predators that can be compared to Elder Dragons. Though very little is known about its life, Abyssal Lagiacrus are feared to be the gatekeepers of the underworld.