His orders - to eliminate all other races from the galaxy, and bring their heads to him!
As Imperator, your objective is to do whatever is necessary to appease your God-Emperor.
This means that defenders can use planetary defenses as additional units to take out attacking ship, and attacking ships will have to destroy any planetary defences before a ground assault can take place. This happens very much like any other space battle, except that planets themselves can have surface to space weapons. The first step in taking over a planet is to take control of the space surrounding the planet. Planetary conquests, however, are a bit more intricate. Pure space battles would happen as you might expect, with the game scaling down into a smaller RTS map where your ships fight it out against the opposing side's ships. One of the more interesting features of IG2 is the interaction between space and the surface of planets. You do this through trade, espionage, research, colonization and most importantly conquest. Like most 4x strategy games, in Imperium Galactica 2 you're tasked with building an empire in an effort to defeat everyone else in the galaxy.
This essentially turned IG2 back into a turn-based strategy game. What this means in Imperium Galactica's case is that you play the game in real time, until it becomes overwhelming, then you slow down and paused the game until you're caught up. OverviewImperium Galactica 2 falls into the rather small family of 4x real-time strategy games.