Trade built Thul Ka into the greatest city in Mugroba from little more than a scattering of villages in the dimly remembered ages before the time of the Book and the rise of the galdori. Merchants in their barges and those coming overland from desert or from scrub stopped at the confluence of the three rivers. There they traded their wares in impromptu markets which, over time, steadily grew more permanent. Houses and inns were built and in the rich alluvial soil farms sprang up. There was little planning in those early days of Thul Ka and streets and buildings went up according to no knowable design. The city grew with the wild exuberance of a a climbing weed, throwing out tendrils of streets to ensnare new lands, swallowing villages and farms as it expanded.
Thorns: Thul Ka is a play-by-post roleplaying game–a form of collaborative writing. Players each create an original character with a history and goals. Players then control their character by writing posts to the forum. Other players, controlling their own characters, interact by writing replies. The result is a vast, multi-threaded story about the residents of Thul Ka.