Perhaps the most commonly seen dire beast, the dire wolf is also one of the ones most visually similar to the original animal. When a wolf transforms into a dire wolf, all its fur falls out in massive clumps, and it gains dozens of pounds in muscle and bone, but it retains the overall shape of a wolf.
The largest change is in behavior. The dire wolf is actually a solitary herbivore, only socializing to mate. Pups are abandoned soon after they are born; they are actually fully grown within a week, so infant fatality rates are surprisingly low. Familial bonds seem to be non-existent, with siblings and children seen as simply competitors for food.
Dire wolves eat all manner of vegetation, especially grass and crops. Therefore, they are pests in the same manner as wild boar, though at least they do not root like boar. They have almost no natural predators among mundane animals (I have personally observed a dire wolf fight off a bear), and little competition among the monstrous species, which tend towards carnivorous.
Ironically, the best way to deter a dire wolf is another dire wolf. They mark their territory much like normal wolves, and avoid the territory of other wolves as though it were plagued. We have had quite a bit of success simply by spraying the urine around the town wall. Thankfully, the smell is virtually impossible for the human nose to detect, so this method provides minimal disruption of the community.
Dire wolf leather, treated normally, is nearly as hard as a weak metal such as brass. If treated properly, with monster materials instead of more mundane tanning tools, it can become nearly as hard as steel.
When fighting one, the first thing to remember is that their jaws are strong enough to bite through steel. That is not even the slightest exaggeration. What is more, they are well aware of this ability, and thus almost always lead with a powerful leaping attack. Therefore, the key is to watch for signs of this (specifically, bracing their feet in preparation for a jump), and then dodge at the last second. If you are fast enough, while they are in the air is also an excellent time to strike back.
Lastly, dire wolves appear to be completely diurnal, with horrible night vision. They rarely, if ever, travel at night, preferring to find a small burrow, nest, or other form of shelter rather than stumbling about blind.