Rogue World

Three planets exactly the same size floated through space. They were alive. And they fed off the light of the stars. When they discovered a new star, they left their orbit for the energy of greater stars. Millennia passed, and new stars burst into existence. And the planets moved slowly toward the new stars like moths to a flame, sometimes taking decades or centuries to arrive.
Planets were knocked out of the orbits they held. These planets were not alive, but the inhabitants were. Many lives were lost as a result of this planetary movement, their populations scattered to the stars.
The strongest beings crafted a plan. They lured the planets out to the farthest arm of a galaxy. They made the illusion of a new star, brighter and stronger than any other in the galaxy. But the planets eventually came to realize they had been fooled, and war broke out.
The planets took the DNA of races they had encountered and combined them to breed an army. The planets combined their energy to send their consciousness, which created wormholes through space, sucking in creatures from other planets.
The war was never ending.
Eventually, there was a great cataclysm. Stars exploded, and black holes were formed. An entire arm of the galaxy collapsed.
The three planets were hurled into space. Their very cores froze. They ceased all consciousness. They wandered the darkest parts of the universe asleep. They traveled so far that they lapsed in and out of time.
They awoke orbiting a young star, hidden and surrounded by millions of dead planets. They had been carried into a dead galaxy with one surviving star. It was young and small, but it was strong. The planets slowly regained consciousness and realized that their surfaces had been colonized by another race from across the stars.
This race was strong and violent. They liked this race. They wanted to use them for revenge on the beings who tricked them. But these samples had flaws. They had sicknesses and diseases that made them unfit. The planets needed fresh samples.