A Hellmouth is a symbolic monster found in many Christian works, especially medieval texts relating to Hell or similar purgatories, envisioned as a gigantic monster with a gaping mouth it acts as the entrance to the spiritual plane of suffering and death; which in many ways it embodies.
A Hellmouth offers a glimpse into the abyss and never closes its mouth, always remaining open as it waits for new souls to fall into it. Often a Hellmouth has many souls visible inside its mouth, struggling to escape but unable to do so as the fiery depths of medieval Damnation consume them.
The Hellmouth is more commonly known as the Leviathan who is also the gatekeeper of Hell. In fact, his very mouth is said to be the gates of Hell, and due to his reputation as the demon of Envy, he lives up to his name as being the demon of Envy by devouring all he desires.
The entrance of Hell is envisioned as Leviathan's mouth is due to the fact that when a whale is hungry, he opens his mouth and a sweet smell comes out. The fish are tricked by the smell and they enter into his mouth. Suddenly the whale’s jaws close. This is similar to a human who lets himself be tricked by a sweet smell and led to sin will go into hell, opened by the devil, if he has followed the pleasures of the body and not those of the spirit.
When the devil has brought them to hell, he clashes together the jaws, the Gates of Hell. No one can get out from them, just as no fish can escape from the mouth of the whale.