The Lurkermantis

Considered the most dangerous land animal in existance, the marshmantis claims swamps and marshes as its territory. Characterized by it's long, wet, slug-like body, giant mandibles which open horizontally to a full 180° as well as a lure on its forehead that is pointed forwards, it has claimed the lives of countless animals as food, as well as carefree adventurers, that ventured into its trap.
Buying itself into the soft soil, head and mandibles aligned to the sky, it lies in wait. Its lure, an appendige that closely resembles as swampberry bush, it waits until something approaches. While in wait, it's soft skin absorbs the moisture in the ground around it to stay wet, as it dies, should it ever dry out completely. This way, the lurkermantis can lay in wait for days on end without moving, only actively hunting, should it be on the verge of starving.
Due to its sheer size, around 20-27 feet in length and a mouth the size of an elephants head, it can catch and eat anything that walks between its mandibles. Should something stand next to its lure, the mouth closes with incredible speed, crushing bones and flesh, regularily snapping their victims in half with the first bite.
As solidary creatures, lurkermantises will only ever leave their territory during mating season. Seeking out a female the males will travel through swamps and mashes to find a female nest. Approaching the female carefully, the male will fertilize the four to six eggs a female usually lays before leaving again immediately. Female lurkermantises will tolerate a male in their territory but only for a short while. Should the male not be fast enough, the female will attack in an effort to drive the percieved invader out of her area.
After around three years, the tiny slugs hatch, immediately dispersing from the nest. Over the span of the next five years their body will gradually transform, their mandibles growing further apart, the lure developing as well as their insides, turning from herbivore to carnivore.