Sulloain Empire

A highly advanced race, the Sulloain Empire occupied a large sector of the galaxy. The greatest concentration of their people inhabited huge capital planets, major hubs for their people. There were about 42 capital planets in the entire Sulloain empire including their home world. Sulloain people also occupied other smaller colonies on other planets, which numbered in the thousands.
Turmoil in their political structure between the capital planets caused the unbalance of their civilization. Each capital planet, like countries wanted power to control the entire empire. It then came to a point when each capital world declared war on each other to fight for control over the entire empire.
The war lasted a very long time, most of the other races just minded their own business since they didn't want to get caught up in the bloody war, and plus in some way were pleased to see that the Sulloains were destroying each other.
Towards the end of the war, the Sulloains used antimatter bombs to literally destroy each others capital planet, and the last planet to be blown to bits was the Sulloain home world, all the other planets, or the smaller colonies where all destroyed by conventional galactic war far. What’s left on those planets is ruined broken down cities that were left by the war, which are now prime relastate for other races to occupy and to plunder what was left of Sulloain technology.