The Oktakalos is a large Leviathan primarily living in Moga Island. It is an Omnivore who commonly preys upon Ludroth for food. They will oftentimes make a small nest on a small stream inland, where their eggs will stay wet. A fully grown Oktakalos can lay 3 eggs a day, and eat just as many Ludroth. Instead of normal bones, they have a high concentration of Cartilage which is used for simple movements such as walking.
As Leviathans, they are related to the Ludroth and Lagiacrus, albeit with much different adaptations.
They are extremely aggressive, going mad if another creature invades it's mating territory. It is perfectly adapted with it's large back shell and horn to fight and kill a Triablos if enraged, and are prone to fighting to death. It is possible that an encounter between an Undead Lunastra could kill a weak Oktakalos, though this is an unlikely meeting.
They've adapted to suck to cave walls when able, and wait for an attackable food source.
A Male has tough shell on the bottom of his stomach, right where the female's spike could jab it. They perform elaborate kills for the female, stacking food as a lure in it's nest. After a female wants to be mated, she may take the bait. She will then take over the nest, laying eggs nonstop until she's acquired 15 of them.