In Dungeons & Dragons, the tarrasque is a magical beast, always featured as one of the most terrible and powerful of creatures. In most campaign settings, only one tarrasque is said to exist on each world. It is neutrally aligned, for despite its violent and savage nature, it lacks the mental capacity to choose between good and evil. The tarrasque was introduced to the D&D game in the first edition of Advanced Dungeons & Dragons. It is based upon the French legend of the tarasque, a fearsome legendary dragon-like mythological hybrid from Provence, in southern France, tamed in a story about Saint Martha. Curiously, UNESCO has included the Tarasque on the list of Masterpieces of the Oral and Intangible Heritage of Humanity. Maybe the Tarrasque will follow.

Physical appearance

The tarrasque is a gigantic lizard-like creature which exists only to eat, kill, and destroy. The tarrasque is very large, 50 feet tall and 70 feet long, and has a Tyrannosaurus rex–like form, although it is much more broad and muscular, with a differently shaped head, and with larger and more developed front arms. It has brown skin, with scabs and warts and bits of encrusted dung all over it which are grey in color. Protecting its back and tail is a thick, glossy caramel-colored shell or carapace. It has spikes coming from its chin, the sides of the mouth, the underside of its neck, the elbows of its front arms, and its shell. The creature also has two horns projecting forwards from the top of its head. The tarrasque’s skin is very hard and thick, and provides excellent armor.

In Eberron

Although there is no official place for the Tarrasque in Eberron, it is mentioned in «Secrets of Xen’drik» as the massive monster slumbering beneath the Iceflow Sea in Xen’drik. For over forty thousand years, it has lain in torpor, imprisoned by the giant wizards of the Sul’at League, and all it would take to shatter the wards and release it upon an unsuspecting world is one careless word mentioned aloud in its presence.

In your campaign

The legendary tarrasque — fortunately, only a single one exists — is possibly the most dreaded monster of all (except for the largest dragons), and is among the most destructive creatures in the known worlds, including yours. None can predict where and when the creature will strike next. Thankfully, it spends most of its time in a deep torpor in an unknown cavern in a remote corner of the world… yet when it wakens, kingdoms die.

When active, the tarrasque is a perfect engine of destruction. It rampages across the land eating everything in its path, including plants, animals, humanoids, and even towns. Nothing is safe, and entire communities prefer to flee the ravening tarrasque rather than face its power. Surround its origins with as many legends as you want: abomination unleashed by ancient, forgotten gods to punish all of nature; conspiracy between evil wizards or merciless elemental powers; sould of the world in vengeance for what civilization ahs done to it. These tales are mere speculation, however, and the creature’s true nature will probably remain a mystery. The tarrasque isn’t in the habit of explaining itself, and it rarely leaves any living witnesses in its wake.

You can take a look at the 5e stats for thee Tarrasque here, and get some cool ideas to customize it from an old 3.5 article here.