Hamilton posted a time line that links the Commonwealth Saga with the Void Trilogy, filling in the 1200-year gap between the two series.
The series includes the following books:
The Void exists as a self-contained universe at the heart of the galaxy, studied by the Raiel for millions of years. The Raiel believe it to be a threat to all life in the galaxy due to its sporadic expansion phases that devour entire solar systems close to the core of the galaxy. One such event occurred several hundred thousand years prior to the time of the story which resulted in the Raiel creating the High Angel class of interstellar life boats designed to carry sentient civilizations away from danger should another expansion phase occur. The Raiel Warrior caste serve to protect the Void from any intrusions by beings of the galaxy as they believe it will trigger another expansion phase.