The "Ugly Dirt Box" is the affectionate nickname for magic-powered starships created by the United Corps of Starfield Travelers (UCST). The UCST, based on Terra, uses many Ugly Dirt Boxes to manage message delivery, trade, and diplomatic connections between the many worlds inhabited by elves, dwarves, goblins, and other races.
When a ship is docked on-world, it looks a lot like someone built a fifth-century dwarven feasting hall in the middle of a bunch of modern government buildings and warehouses, but with less character than an actual feasting hall.
The Ugly Dirt Box Universe is 'modernized fantasy' - a 'magitech' environment created when a standard high-fantasy realm of magic-using creatures reached a technological breakthrough, causing the organic development of magic-based technology to allow them to travel the starfield. After ten thousand years of development, many worlds are inhabited, many different types of technology have been invented, and millions of folk live in individual variants of 'peace and prosperity' (meaning there are still lots of fights).