Goblin

They had pale grey skins, huge bat-like ears and were much shorter than a human. Their arms were very long, to the point that they could touch the ground if they crouched, and most of them were very thin. From what he could see of their faces, they had somewhat square faces, with flat noses and big mouths, and two big, bulgy red eyes. They were also completely hairless.

They have 4 fingers as opposed to 5 (Ch. 30).

Goblins had always been a tribal race, usually not having any settlement bigger than a few hundreds but that all changed under Trakk who united multiple Goblin tribes under him as they fled from the Orc Horde. They are usually pretty territorial and it's hard to make them move, but under particularly dire circumstances they are known to migrate en masse. They are quite aggressive, and are known to attack anything that approaches their nests.

“To them, goblins are a race of uncivilized barbarians, no better than animals. They may be cautious towards us on an individual level, like they'd be cautious around a wolf or a bear, but as a whole they don't take us seriously. And being underestimated is perhaps our greatest advantage towards them!” - Trakk on human perceptions of Goblins as a threat '''Chap. 42'''

Racial traits
Goblins had very good night vision, not perfect but they didn't have any trouble seeing about 30 meters away even in the middle of the night (Ch. 20).

Goblins reproduce at a very fast pace. Moreover, they appear to be capable of transmitting their acquired traits to other goblins in some way. Ch. 46

Evolution
When facing and surviving a dangerous enemy, the goblins can copy the characteristics of that enemy. This is why the goblins can be so different from each other: depending on the enemy they copied, they could appear completely different!

Goblins have been revealed to only copy the traits of the enemy that scared them.

Variants

 * Hobgoblin is the name of goblins who have evolved after any humanoid species in general (humans, orcs, elves, etc). For example, "human" goblins are called human-hobs, while "orcs" goblins are called orc-hobs. Those "basic" hobgoblins can potentially undergo a further evolution, though it's very difficult. For example, an orc-hob could evolve into an ogre-hob. Meanwhile, human-hobs can evolve into more job-like forms, imitating the skills of a specific human, like an Aura Master (in that case they become Goblin Champions ) or officer (Goblin General). In the case of Trakk, he was born as a normal goblin, then became an human-hob and finally turned into a Goblin General.
 * Shamans are a separate evolutive branch. They are goblins who were scared of the natural elements (earth, lightning, fire, etc) and developed some instinctual control over them . Shamans are "tied" to a specific territory and are basically powerless outside of it. They basically form a "bond" with the elemental spirits of a certain place and can summon them to do their bidding. But forming a new "bond" in a new places is very difficult, and it may take years. Inside their territory shamans are very, very powerful.
 * Gargoyles are goblins that have been scared by dragons

United Goblin Tribes
The UGT is not just the largest host of goblins ever seen since the time of legends. It’s also the majority of the goblin survivors of the Caligare Forest. Most of the goblins inside the forest have died, and the survivors fled to the north, where they have banded together under Trakk's rule. Together, they managed to resist for a while, but the forest was not a good place for any civilization bigger than a few tribes. The territory was not suitable for farming, and they were going to exhaust their sources of food pretty soon. Which meant that they had to move somewhere else. A place where they could actually cultivate the land and form a peaceful, civilized society. '''Ch. 64'''

Trakk is exploiting goblin evolution mechanics by keeping dangerous beasts caged and chucking in new goblins. He makes it so that a few always get out alive while there are enough casualties to really trigger the evolution in the survivors.
 * Trakk - Goblin General in charge of the United Goblin Tribes
 * Grel -  he is a Goblin Master and Trakk's second in command.
 * Arag - the only one of his breed in the whole army, a Spider Goblin.
 * Ureg the Scarred - the strongest Goblin Master of this army and the commander of the assault forces.
 * Grom the Basher - a humongous Ogre Hob acting as the commander of the Orc-Hobs.
 * Shak - the biggest Gargoyle of Trakk's camp.
 * Klatch - the leader of the Goblin Shamans

Great Goblins of the Past

 * Kalagon the Red - led a legendary raid more than thirty years prior to the story. Despite its place in Goblin history it's just a footnote in human history with it being unlikely many still remember it (Ch. 42). This is likely the raid that killed Felix's great grandparents and left his grandparent destitute (Ch. 46).

Female Goblins
“Most of them carried the provisions that were the lifeline of any marching army, but some others carried something even more valuable. Those carts, which were visibly more comfortable and secure than the rest, draped in tents and being pulled by very well mannered orc-hobs, literally contained the future of the goblin race. Carrying them with the army during a raid was extremely reckless, and was something no one ever did. But the stakes had never been this high, and Grel understood why the General insisted on bringing them” (Chap. 41).

Role in Goblin Society
On the contrary, goblins in my setting are very much sexual and in fact are technically a matriarchal society.

The females are kept safe. They don't go near battlefield, hunting or whatever... they stay hidden in the safest part of any goblins den and goblins are ridiculously protective towards their females. Even the most cowardly base goblin would fight a dragon to protect a female goblin.

Well, first off female goblins don't really care, and they live in luxury compared to other goblins and don't suffer psychologically from being secluded like a human woman would.

Second, they don't have the evolution magic of male goblins. They are naturally smarter than base goblins, plus they have a moderate regenerative capability (pretty much on par with Marcus) that makes them incredibly resilient (so that frequent childbirth is not a problem for them, as they are incredibly fertile). Female goblins can live up to 230 years (and are fertile and young looking for most of their life) while the life expectancy of a male goblin is much shorter.

Oh, and finally the male goblins are UTTERLY devoted to them. If the females decided to have Trakk killed, they could order Trakk to kill himself and he'd most likely obey.

Appearance
It depends... do you consider Midna from the game Zelda attractive?