The Rihal Imperium is or was one of the longer-lasting Empires of Innworld, existing over fourteen thousand years before the story's start.[1] Its exact whereabouts have not been a topic so far.
The Rihal Imperium had a magical tradition at least six hundred years old when some of their spellcrafters created the three hundred year old spellbook that was in Teriarch's possession. He owned a first-edition copy, which indicates that Rihal had abilities to mass-produce "editions" of these books.[2]
The name Rihal was unknown to Krshia, when Ryoka handed the book to her.[3] This means that the Empire might have ceased to exist at some point after the book was made; or that it still exists in a far-away part of the world, possibly Chandrar.[4]
The Rihal Imperium once bred Garbichug Revolters as war animals, to use against the Putrid One. This backfired when The Putrid One made them multiply and used them to spread minor plagues, and the Rihal Imperium earned international censure.[5][6]