List of Empire States from official website.
To reflect the internal state of the empire, each empire always has a high level state. This impacts a lot of things but most importantly how aggressively it attacks, how quickly it researches.
Empires can change states every 1000 cycles (~1.5 minutes) and do so quite randomly.
When an empire is EXPANDING, it will obviously try to expand it's borders, by attacking other stars. They do some research too.
All empires start out like this, and it's usually pretty solid.
When an empire is FORTIFYING, it is trying to solidify it's border and focus on internal development. They will still defend lost stars quite fiercely, but rarely (though sometimes) conquer new stars. Research will be about twice as efficient as an EXPANDING empire, and stars will develop faster.
FORTIFYING empires tend to beat out EXPANDING empires if they are lined up against each other. But if they are both starting out with a lot of room, then obviously the expanding empire will grow much faster and probably even out-research the fortifier and then quickly kill it. It's often an interesting fight.
This simply indicates that the empire has had enough for some reason. It has lost the collective will to do anything useful. Maybe they are simply lazy after dominating the galaxy for hundreds of years, or maybe they are busy filing paperwork in an explosive bureaucratic nightmare.
At any rate, DEGENERATING empires do not expand or defend lost territory. They do not research, and in fact they may lose technology (maybe the priesthood decide they don't like it). They also blow up artifacts left by ancient civilizations (or themselves).
An empire may bounce back from this to fortify or expand, but they typically find that the galaxy is now filled with lots of small upstart empires that have eaten up most of their territory while they were on vacation. Oh, and those upstarts still remember how to build plasma guns ... Have you seen the blueprints for them lately?
In this state every star of the empire leaves the galaxy and enters some kind of utopian dimension. Normally, empires transcend when they reach tech level 9.
Well something is clearly going wrong now. Perhaps some scandal in the court has outraged the plebeians to rise, or maybe it was the construction of that gigantic lunar monument with tax payer money that tipped people over the edge.
In any case, every single star in the empire is now at grave risk of revolting to try their own hand at interstellar management. Those stars still loyal will bravely fight to get the empire back, but unless the prince apologizes for that faux-pas in the sauna, to stabilize the regime, their outlook is grim.
ALL WILL BE ASHES Edit
This is a rarely seen thing, but it can be quite spectacular.
For some reason, they have now decided that they have to rid the galaxy of all life, including themselves. Maybe they got really bored, or maybe it's just a bit of the old fhtagn! kicking in.
They will launch a spectacular attack, boosted by their fanatic beliefs, in an attempt to conquer stars. But once a star in their empire has become developed, they blow it up ... Including of course any stars they own when they collapse into this state of mind.
So the result is basically that they never have a core in their empire, they simply blow everything up and control only some stars in the front lines that they are continuously trying to expand. The vacuum left from their scorched space policy creates a great breeding ground for new empires. But of course, if the ALL_WILL_BE_ASHES empire finds it's way back, it will simply get more fuel to continue on with the rampage.
This can go on for some time, like a wildfire constantly looking for new fresh worlds to conquer and blow up. Or it can just fizzle out very quickly, but usually it's quite fun to watch.
There is no turning back from this state.
Well family is always the worst, right? Empires who enter this state have simply decided that there'll be no more awkward family dinners or drunk cousins at weddings. They all have to go.
Blood purgers will wage manic war against those who share a common ancestor with them, though be very reasonable with everyone else. They get a combat bonus, and are remarkably stable in that they simply want to end their bloodline once and for all.
Now, once they are done, and they no longer have any family around, there's not much more for them to do. Maybe they will simply Transcend to celebrate, or maybe they will turn inwards and realize that the blood of most hated enemy still lives ... Within themselves ...