Humans in fact are not native to the islands. They came from a continent called Aphasia many hundreds of years ago as refugees, as Aphasia was destroyed or at least made uninhabitable by some unknown doom. Varchia was originally populated by orcs only, who are native to the area. When humans first arrived a war broke out since the orcs of old were xenophobic and warlike and human's weren't too nice either. After a long conflict that halved the populations of both races a period of uneasy peace followed, but eventually humans and orcs started cooperating and trading, which is how it is at the present day. Humans also brought wolves and dark oak trees from Aphasia, neither of which were native to the islands. For some reason though, the dark oak trees only manage to grow on the south coast, as they are sickly and weak everywhere else.
Humans have a deeply stratified society with hereditary dictatorships (aka kingdoms) ruling plots of land, or at least oligarchies composed of noble houses. While the influence of noble bloodlines is somewhat weaker than it used to be, it remains pretty strong in “civilized” human lands. Humans used to practice slavery (i.e. chattel and domestic servants), but it got abolished sometime ago. Many former slaves still serve their former masters though, because they don’t know any better. Also indentured servitude is still a practiced and many crafty merchants are trying to lure their employes into debts so the later would work for free.
Humans are the most well-rounded (i.e. boring) species inhabiting Minearchy without any specific weaknesses or strengths. Human nobles however tend to suffer from nether wart intolerance (likely due to marrying too many cousins) and conventional potions are ineffective on them, so they have to use special homeopathic potions.
Cult of ancestors - most of these people worship the spirits of their forebearers, especially the Great Aphasian Dynasties. While many rulers and nobles build glorious mausoleums to appease and exalt their ancestors, most of the common folk is content with quiet sermons near the resting places of their parents and grandparents.
Very widespread, can be found practically anywhere.