Lesser Saxum Wurm
Saxum wurms are massive tectonic serpentine monsters. Unlike regular wurms that tunnel through soft topsoil or dwell in forests, saxum wurms are a vicious variety that prefer rock and mountain. They are distinguished by their spiny black plates, slowly formed over decades of consuming metals and stone. They enjoy slumbering underground in valleys or in volcanic environments for massive stretches of time, often basking in the pleasant heat of fissures, vents, and flowing lava. Suffice to say, these wurms are nearly immune to the poisonous gases, heat and pressure of these environments. Many travelers pass them by without realizing, as a sleeping saxum wurm blends into the obsidian and cooled lava well.
They do not “hunt” so much as erupt. A saxum wurm senses vibrations and mineral-rich blood from far below, then drives upward in a catastrophic surge. Despite how dangerous they are, saxum wurms usually pose little threat to the average denizen. Wurms require a lot of vibration above ground to awaken them, and provoke them to emerge. This also helps serve the purpose of finding ideal prey; herds of animals, and other giant beasts and monsters.
Saxum plate fragments are extremely extraordinary and prized materials. Pieces are sometimes chipped off during battles or digging. Saxum plates from older and larger wurms are exponentially more difficult to melt or work with, but they take well to red and black mana. The material makes for some of the hardest and most durable weapons, armor, and tools should a skilled enough craftsman succeed.
It goes without saying that battling one is a task suited for only the most powerful beings. Conventional weaponry and manpower may overcome lesser saxum wurms to a point, but that becomes less untenable as they mature. Then, only other great beasts, monsters, magic users, and planeswalkers pose a threat. Repelling them is a possibility, but saxum wurms grow stronger and more bold with age, and are more likely to fight to the end.