The Thertian Empire is not really an empire, but their neighbors call them an empire. They are an extremely high tech civilization whose home star is unknown but probably somewhere in the region of space they call their own. Their species is humanoid, but it’s unknown if it were ever homo sapiens — there has been so much genetic engineering that whatever their original species was, it’s not known now. They have extremely effective AI’s. Their spacecraft are extremely automated, with robots and AI’s handling every task other than setting overall strategic objectives. A Thertian Deathbird is roughly half the size of a Hanoverian Battleplate, but probably has twice its fighting power because there’s only a dozen or so humans aboard, leaving the rest of the space for more missiles and laser pods. They find the Hanoverians to be somewhat… rustic… and don’t quite understand why the Hanoverians staff their spacecraft with so many humans.
You don’t enter Thertian space. If you do, you leave quickly, or are destroyed. They have trading outposts outside the edge of their declared sphere but only Thertian merchants are allowed to travel from there into the Empire itself. Their system of government is unknown but appears to be some sort of anarcho-socialist collective mediated by the artificial intelligences. It is unknown how many Thertian Deathbirds exist.
The Hanoverian Confederation has decided to open the Thertian Empire to Hanoverian traders via sending half their battle fleet protecting a number of trading ships. They are about to find out how many Thertian Deathbirds exist. The hard way.