Osentia the Earthen Beast
Size: 400 feet long, 50 feet wide
Threat: Low (when sleeping) to CRITICAL (when awake)
Location: Underneath and inside the Ascarlin Mountains
This creature is an ancient, earthly monstrosity that slumbers under the mountains west of Negav. It is more of a serpent-insect hybrid than anything else. (don't wanna say dragon, since that may offend some people).
It wields large scythe strength pincers on the side of it's mouth and bears multiple rows of teeth. It's eyes are intensely powerful, being able to see thirty miles away at the least. The claws span large enough to pick up a full grown naga and throw it in the air. It's thick hide is covered in the hardest rock substance in all of Felarya, making it a worthy opponent in battle. Osentia is immune to certain magic, and resistant to offensive spells, meaning that mages will have little luck dealing with the creature.
The creature has two warning levels which represent it's current state. When Osentia is asleep, the level is low, for nothing will usually disturb it. The beast usually sleeps miles underneath the mountains in a near endless slumber. It's body, which spans very long distances, stretches in and around the mountains. Rumor has it that the beast's body could span out under other areas too. Try as you might, you will not be able to awaken Osentia, since it sleeps like a rock.
It only awakens once every three months to feed. However, when this day comes, every creature within the vicinity is in danger. Osentia arises from the rocky terrain a hundred feet into the air, planting both of it's claws firmly on the ground. The creature will then proceed to feast on any predators in it's range. Nothing is spared from it's voracious appetite. Nagas, humans, harpies, and even elementals in the area will be consumed, should they be caught in it's grip. For some reason, it doesn't use it's teeth when devouring prey. In fact, they are rather out of place in Felarya, and may have only been useful in the world where Osentia was originally from.
Some people worry that the beast will escape and destroy Felarya. Fortunately, this is unlikely. It's body is too intertwined into the mountain to allow it full movement. He is only capable of grabbing prey within his zone. Unfortunately, most of the mountain is his zone.
The reason it has such a high level of threat is because practically no army can defeat this titanic beast, and should the creature ever try to leave the mountain in search of other food sources, the guardians are the few, if not only ones, that can put it back to sleep.
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I hope this beast is to your liking. I tried not making it too powerful, giving it limitations and all. However, you never quite see those "really dangerous" predator eaters out there too often.