Unicorns are mythical creatures first created on The Land in LY 577. They were genetically engineered primarily from white striders (using the shortest ones the Sorreters could find, in the hopes of making unicorns closer to the size of Terran horses). Genetic material was also included from monoceroses, the tusks of which were modified to grow out of the unicorns' heads as a horn.
In 580, Sorreters began relocating various species of mythical creatures, including unicorns. While most of them were moved to the Drop Lake Mts. and the Southern Range, two mountain ranges in the southern part of First Land (well-removed from any human settlements), others were moved to Tanq Forest. It was about two decades after that that Tanquers first became aware of unicorns, and began hunting them, to use either as mounts, or to harvest their horns (which are called "alicorn," per Terran tradition). These horns may be made into goblets, or ground into powder, which may be used as a drug for various purposes, such as curing disease or bringing good luck. There is no evidence that alicorn powder has any such effects, though it was popular for several centuries, until the passing of the Sentient Rights Act in 913. However, it is believed that the first generation of unicorns were taught by the Sorreters who created them to mentally mix their chakra into mana, so they could do some simple magic. It is further believed that unicorns used this magic to cast spells through their horns, which explains the belief that alicorn powder might contain trace amounts of mana, which would give it magical properties.
When the intelligence classification system was introduced in 774, unicorns were among the species of mythical creatures which were deemed "semi-intelligent." The fact that they had a degree of intelligence was later further demonstrated when, during the Coming of the Order, some unicorns provided help to the Protestant Movement, having been promised by Drag and his allies that they would try to put a stop to the hunting of unicorns, if they managed to win the war. Of course, the Protestants lost, and so hunting continued until 913, when the newly established United Villages of the Chaos (of which Tanq was a member village) passed the Sentient Rights Act, by which all erstwhile semi-intelligent creatures were granted equal status as fully sentient beings.
It is rumored that some trafficking in alicorn powder may still be done through the Illuminati, whose don in Tanq, Lydia Hornpowder, comes from a clan which had long been among the world's leading suppliers of the product, before the new law was passed.