A very rough sketch, quickie ref sheet.

Background:

Trolls are an artificial species, a mix of human and native Caranoctian reptilian mammals, created by the Aelvians to be physically tough, highly intelligent slaves. It didn't quite work out - the trolls rebelled, slaughtered their creators and destroyed their city, Thorcasia, and escaped into the wilderness. Now that the human-Aelvian war is over, they've begun trying to decode Aelvian magic for their own use, and are gathering information on the new pan-species society (whether to join it or conquer it, no one but the trolls know).

Anatomy:

Compared to the average human, trolls are gawky-looking, with corded, stringy muscle and knobby joints. Their sloped shoulders and slouching posture make them seem a bit shorter than they really are. The arms and torso are longer, especially the forearms, and the legs shorter, especially the thigh. They walk and stand with the heel touching the ground, but raise up on their toes to run (this one is shown in the digitigrade pose). The tail is very flexible, but not prehensile, and shows mood, similar to a cat's.

There are four digits on the hands and feet. The middle toe is the longest, the first toe is set back like a dewclaw and slightly opposable. Claws do not retract. The wrists, elbows and heels sport curved spurs which are made of keratin and can be trimmed down. There may be smaller, extra spurs along the back of the arms, legs, and on the spine.

Trolls are more reptile than mammal - no nipples, no navel, no sweat glands, no facial or pubic hair, and very sparse, straight body hair. The skin is covered in grainy scales dotted here and there with larger, bony scutes. There are often iguana-like spines on the edge of the jaw, chin, bridge of nose and eyebrows. Hair is very thick and lank, almost more like flexible quills, and runs down the spine as a mane, tipping the tail in a tuft.

Skin color is usually some variation of yellowish-greenish-gray, dull slate blue, or terracotta, with darker or lighter mottling or other markings, including patches of cobalt blue. Hair can be black, rusty brown, orange or very dark blue, often with a lot of gray mixed in. Rare albinos have light blue or white skin, and blue or white hair (blue is a structural color, not a pigment, and unaffected by albinism). The sclera (white) of the eye is black, the pupil round, and the iris comes in pale shades of gold, orange, gray, blue or green.

On the forehead is what appears to be a dark reddish-black jewel, smooth and oval, set into the skin. This is actually a parietal eye. No lid, no pupil, it is mainly used to sense infrared light.

Trolls all have very similar facial features, probably because a single human was used as a model: low forehead, narrow, close-set eyes, prodigious aquiline nose, wide, thin-lipped mouth, sharply angled jaw, hollow cheeks and pointy chin. Some appear almost human, others are more feral with prognathous jaws. The teeth are all sharp and rather crooked (they are continually replaced, like a reptile's). Older trolls have fewer, bigger teeth with more gaps. The tongue is long and purple with a forked yellow tip, the saliva mildly poisonous.

Trolls have a single gender (isogamy) - they aren't hermaphrodites. The genitalia are located where you'd expect, hidden behind firmly clasped-closed folds of skin. To humans, they all appear masculine, but in fact both partners will come away from a romp pregnant. Newborn trolls, trollspawn, look like hideous, reptilian kittens and are able to run and hunt almost from the start. When they're able to walk upright and imitate speech a little, they're called imps, and remain so until sexual maturity (about age 10).

Psychology & Culture:

Trolls are aggressive carnivores. They tend to band together in structured troops, but are rather asocial and squabble constantly over rank. The two most dominant will usually be the only ones in a troop who breed. They can, however, be surprisingly tolerant and kind towards infants and others who are obviously helpless and unthreatening.

Trolls are extremely intelligent, more so than humans, logical, stubborn, systematic, quick-thinking and inquisitive, but not terribly creative. They don;t enjoy fiction or abstract art and their music is mainly percussive. Their clothes are dull and practical, tight fitting on the torso but loose on the limbs to allow freedom of movement, and usually with high, stiff collars (during fights a swipe of the wrist spur to the throat is a popular move). They almost never have piercings, jewelery or other decorations.

Oddly, trolls tend to either be very loquacious or extremely taciturn.

Currently most trolls either live in the deep swamps of Guldurgu where they hid during the wars, or in the ruins of Thorcasia, where they research the lost magic of the Aelvians.