The Shellmouth are hostile hulking humanoid-like figures that can be found in the Frontier. They are often compared to a Whapper and the Forest Guardian. They are usually reported to be seen on the coastlines of Coral Bay.
It also makes an appearance on the 11th floor of the Otherworld Tower, Lost Brothers, serving as main obstacles as the players progress through the dungeon.
It is described to be similar in structures of a Whapper or a Forest Guardian, except that it has blue skin and its face is occupied by a Shellmouth. It wields a dead coral "tree" as its main weapon.
There are three attacks that the Shellmouth can perform:
Bash - Attempts to bash the player's head in front of itself.
Swing - Swings its weapon in front of itself.
Swipe - Swipes the players in front of them with its arm.