Illium Empire:
Appearing from nowhere many years ago, they came over from the Delta Galaxy when the Light Bridge connected the two galaxies. As the Suisen Empire and the Illium Empire became allies and Ao married the leader of the Empire, Avictius Hsunde, all seemed to go well until the Illiums took Ao's son, apparantly killed Ao, and kidnapped Erevis and took over the Suisen Empire, and then the Alpha Galaxy.
The Illiums are tall beings, usually 7-8 feet tall, with glittering skin in sunlight or bright light, and have diamond skeletons without the weaknesses most diamonds have unless one damages their bones enough. Their weakpoints are naturally the eyes and joints, typically. They take on electricity well and other magik, so it comes down to brutual force, or things that can shatter diamond.
Their normal armada so far has finally been cracked, though new battle stations, like the Battle Cube, have appeared, and the living armor, show that they have more. And it's clear there's a definite divide in worker classes - the noble class rules over all, with the warrior class being next, and then engineers and workers following next, and lunch ladies on the bottom.
Many Illiums that have turned over to the ally sides seem to not remember much about their past, strangely, and cannot tell more other than the last 10 years. To learn more, they will need to go into the heart of the Delta Quadrant.