Terrasque

The terrasque is a gigantic creature that lives off the southern coast of the Confederacy of Andalus. It disappears beneath the surface for years at a time, surfacing occasionally to wreak havoc along the shore before once again returning to the sea. Despite the terrasque's longstanding and outsized presence along the coast of Andalus, much about it remains a mystery because it is so dangerous to study. Its origin, its motivations (if any), and its habits when it is beneath the water are unknown. Despite this, the government of Andalus has developed methods of detecting the terrasque as it approaches land and rapidly evacuating those in its anticipated path.
=== Biology ===
Though much of the biology of the terrasque is speculative, a few researchers have gotten close enough to the creature to make reliable observations.
It appears to be reptilian in nature, and presumably can breathe both air and water. It is approximately 350 feet tall and 500 feet long. Its head resembles that of a lion, though it has dark green-gray skin instead of fur; it has a heavy, square muzzle and the massive fangs of an apex predator, and its eyes burn an amber yellow. It is a hexaped - it has six thick legs, all tipped with sharp claws, and it moves on land with a rolling gait that resembles a bear's walk. Presumably in water it can use all six limbs when attacking, but on land it requires four legs on the ground to remain upright.
The terrasque has a thick carapace that covers its back and flanks, akin to a turtle shell, though not as bulky. This carapace repels almost all attempts to injure the terrasque. Barnacles, corals, small crustaceans, and other invertebrates make their home on its back. Its tail is long, muscular, and surprisingly flexible, and it is tipped with a wicked stinger. It is unknown at this time whether the stinger contains any sort of venom - this adaptation would seem unnecessary in such a large creature, but there isn't a clear reason why it would have the stinger otherwise.
When the terrasque nears the surface of the water, and while it is on land, it creates a localized storm. Heavy rainfall occurs in about a ten-mile radius around the terrasque, and frequent lightning strikes occur in about a five-mile radius. Strong winds swirl in a counterclockwise fashion in a one-mile radius around the terrasque, strong enough to tear up trees and blow down small buildings. However, the air in the immediate vicinity of the terrasque is deathly calm. It's unclear whether the terrasque intentionally creates this storm or if it is a natural reaction to some element of the terrasque's physiology.
=== Behavior ===
The terrasque's behavior is even more notorious - and more baffling - than its biology. How it spends the majority of its existence is unknown; attempts to track it beneath the ocean for extended periods of time have failed. It seems to make its home in the seas south of Andalus, and, as of yet, there is no evidence that it makes landfall in other parts of the world.
The frequency of its landfalls varies, but is generally once every four to ten years. Occasionally it will remain beneath the ocean for as long as twenty years. There is no recorded instance of it making landfall more than once a year. When on land, the terrasque moves in a slow, arcing path inland and then back to the ocean; its total time on land can last between three and fourteen days. It has never traveled more than 40 miles away from the coast, presumably because it cannot spend too much time out of the water. It most often makes landfall in Castillia, Virya, and Hamza, though all regions have experienced at least one landfall in history.
While on land, the terrasque tears deep gouges into the ground, literally reshaping the landscape. Rivers have changed course, new lakes have formed, and cliffs have collapsed (while new ones formed) due to its behavior. Some researchers hypothesize that the terrasque is consuming some sort of mineral or other substance found in the earth; however, the evidence available is limited to unreliable eyewitness accounts and interpretations of the gouge marks left in the terrasque's wake. The terrasque does not intentionally seek out towns and cities, but neither does it avoid them; it's unclear whether it even comprehends the difference between constructed buildings and natural geological formations.
The terrasque ignores the majority of attempts to injure it, presumably because its carapace, thick hide, and massive size protect it from genuine harm. However, there have been a few instances where a team attempting to gain its attention actually succeeded; in these cases, the terrasque has lashed out violently against the people who wounded it. If, in the course of its attack, it changed the direction it was facing, it would then continue in this new direction once it perceived that the threat (or, more accurately, annoyance) was past. This suggests that the terrasque's path on land is essentially random. It also means that one can change its path; however, the risk involved in any such attempt vs. the likelihood of success makes this strategy of dealing with the terrasque infeasible.