The Empire spans across large parts of the milky way galaxy, with Earth currently on the very edge of its reach.
There are several ways a conquered planet is used by the Imperial government. First, the planet, if inhospitable to Alternian life, must be terraformed. This includes planting Alternian species of plants and animals, and changing the composition of the atmosphere, sometimes installing one wholesale. After the planet is hospitable, citizens are shipped to colonies and the planet is officially declared part of the Empire. Generally, a planet will only have one major export, which will fall into one of three categories.
These are Brood Planets, which export trolls - bodies to go to the other forms of planets, Farming Planets, which export food and material goods, and Scholar* planets, which export knowledge and technology.
Scholar and plantation planets are often the largest in terms of land actually livable, but have the lowest density of populations. Brood planets, much like Alternia itself, have something of a catch-call society, with minor industry and agricultural cultures only to support the local caverns and whatever companies choose to place down roots there.
Alternia is in the center of the Empire l, but the planet holds very little importance in the politics of the Empire. Instead, it's considered a very minor Brood planet, with its main export being live bodies for the Army and Navy.
Trolls from Alternia are generally considered to be weird or odd, as their upbringing is very different from the norm of the rest of the Empire. Alternians are both considered incredibly martially adept, but lacking in some social graces. Sort of like that person you may know who didn’t graduate highschool, but is insanely good at mechanics and practical knowledge. A bit of a ‘sure, you got that fancy degree, but I graduated from the school of hard knocks’. You don’t really argue with it.
*’Scholar’ comes more from the fact that these on-soil cities hold a large amount of material collected over the millennia from artists and scholars, usually mostly highbloods. These planets however, are also host to most of the factory and industry in the Empire, with a great deal of the higher learning based on the ground there going into engineering and construction.