The Kaleidoscope System
This star system is home to three sapient species. The planet Chryphóra/Qentora is populated by bipedal, land-dwelling fish at an early industrial stage, torn apart by a long-lasting conflict between two superpowers. Ranul, a moon of the planet Kasavoa, is inhabited by an advanced society of reptilians. They learned the hard way how devastating such a conflict can be - and yet, some already start forgetting that lesson. Finally, on the outermost planetoid you can find Those Who Know - a vaguely insectoid race, united in an ancient hive mind and looking on the younger species in concern.
One defining feature of this system is the cosmic phenomenon which the Chryphórans call the Kaleidoscope. Located at the outer edge, this colorful nebula bombards the system with a wide range of electromagnetic radiation. Said radiation affects the whole system to various degrees. It causes occasional mutations in Chryphóra's lifeforms, it provides power to the technology on Ranul, and it enables Those Who Know to manipulate matter on the subatomic level.
Finally, there is another group who visits the system every couple of centuries - a herd of sentient, organic spaceships roaming the universe. Mostly unseen due to their camouflage capabilities, they stop by the worlds which harbor life in order to feed on various plants and minerals. However, the last time they came here, one young ship got left behind, creating unexpected connections between various parties throughout the system...