Trolls are large humanoids with long, ungainly limbs. They stand between 9 and 13 feet tall on average, though their height is somewhat disguised by a tendency to walk hunched over, and they weigh upwards of 500 pounds. They have large hands, with long fingers and even longer claws, and their hide is thick and rubbery. Though they are less intelligent on average than humans, they are still sentient creatures that are capable of rational thought and reason, but their unique metabolism means that they are often hungry and this can drive their decision making.
Trolls are one of the few sentient creatures that can be found anywhere on Eberron. They can be found on all four continents, and there are even varieties of troll that live in the ocean. Their origin is unclear, and they are a relatively solitary species, living alone or in small family units. Despite their widespread population, they are not particularly numerous, and in Khorvaire specifically they have mostly been pushed into the fringes by the other races. The highest concentration of trolls on Khorvaire is in Droaam.
Trolls are most well known for their incredible ability to regenerate. Trolls bodies heal at an alarming rate, flesh knitting together over wounds and severed limbs reforming in minutes. This makes trolls extremely durable, they are practically impossible to permanently harm unless they are targeted with specific substances that hinder their regenerative abilities (or occupy them.) In addition to this supernatural hardiness, trolls are incredibly adaptable to essentially any environment. It is possible that the speed with which they regenerate also provides room for rapid mutation, and trolls generally change to become better suited to their environment. Trolls that live in colder climates grow fur to keep warm, for example.
In the Barrens, trolls would often dominant groups of smaller creatures and establish themselves as chibs. In some regions of Droaam, this is still the case, especially around Turakbar's Fist. In the rest of the country, trolls have more or less assimilated into the society of Droaam, performing heavy labour or serving in the country's military. Trolls who are too disruptive to society are sent to work at the grist mills, so most trolls in Droaam are generally fairly well behaved. By and large, the trolls of Droaam have learned to view the smaller denizens of the barrens as smaller siblings, and while they might smack them around a bit to establish dominance, these altercations are unlikely to end in a death. That said, trolls expect to be treated with respect by smaller creatures, and they won't tolerate insults. This is a well known facet of their behaviour, and if someone is killed after deliberately antagonizing a troll, this isn't viewed as a fault on the part of the troll, but rather as an elaborate form of suicide.
Trolls are proud of their strength, and they respect strength in others. They enjoy engaging in tests of strength, games like tug of war, weight lifting, or wrestling with other trolls, ogres or minotaurs. Whilst they are generally dismissive of smaller creatures, they are impressed by anyone that performs remarkable feats of strength in their presence.
Scrags
Given the extreme adaptability of trolls, it's not too surprising that they are also able to adapt to living underwater. Scrags are trolls that have mutated to be able to survive under the water, and they can be found in the sea and in underwater caves around Khorvaire and Xen'drik. Scrags are excellent swimmers, and have not only developed gills to allow them to breathe, but also fins on their limbs to aid in movement beneath the waves.