Cassidy III is a blueish-green world that was discovered at the beginning of the 26th century. It has a large amount of Forerunner technology and structures present on it's surface. The technology on Cassidy III renders the planet undetectable by space scanners and sensors, causing it to be very hard to find.
Initially, the Unified Earth Government discovered the planet, but it was deemed too costly to become a colony. This was due to the fact that the old slipspace drives of the time would require a large amount of fuel to reach the planet. In 2508, a pirate captain was in the middle of a space battle after trying to plunder another ship, he retreated through slipspace and arrived at Cassidy III's location purely by accident. The captain and his crew would be the first to settle the planet. The settlement they founded was called The Hole in the Wall. Later, the pirates would also begin to create ties with Insurrectionists who were seeking refuge from the UNSC.
During the Human-Covenant war, the UNSC would find the planet once again the same way the pirate captain had, by pure accident. ONI probes were sent to scan the planet to spy on the inhabitants partially because it was known that the rebels on the planet were safe from the Covenant due to the planet's invisibilty to sensors. When the Covenant found Earth in 2552, one of the UNSC's backup plans was to move many assets to Cassidy III if Earth fell to the Covenant.
The fall of Earth would never come and the Human-Covenant War would end in 2553. After the war, the residents of Cassidy III would become a part of the United Rebel Front. ONI would classify Cassidy III and it's sole settlement as top secret and decide to not disturb the planet's population. However, ONI did continue to spy on the planet without the Front realizing that the planet was now known to the UNSC.
- Main article: The Reclamation
In 2558, the Reclamation would begin and cause most of the UNSC and the URF to be under Cortana's control. The remant of the UNSC would be in hiding. ONI would task Alpha-Nine to go to Cassidy III to contact the residents of the Hole in the Wall in attempt for the UNSC and Front forces to unite against Cortana. Alpha-Nine would achieve this goal and they would use the AI, Vergil, to try and discover how the Forerunner technology had kept the planet concealed for so long. However, soon after Alpha-Nine had made an agreement with the Front leadership, a fragment of the turned AI by the name of Leonidas had followed them and revealed the location of Cassidy III to Cortana.
Battle of Cassidy IIIEdit
- Main article: Battle of Cassidy III
Almost immediately after the treachery of Leonidas had been revealed, a Guardian appeared in Cassidy III's atmosphere just above the Hole in the Wall. It immediately sent an electro-magnetic pulse throughout half the planet, causing all electronics to go dark. Forerunner soldiers then began to teleport with the Hole to fight any resistance within the settlement. With the help of Vergil, Alpha-Nine and the Front forces were able to reboot the power for the Front's ships. Front piloted Broadswords that were stationed on the opposite side of the planet arrived and led the Guardian away from the Hole. This provided a window for all the ships to escape with most of the Front leadership and scientists stationed at the Hole on board. A large portion of the citizens had to be left behind.
In order to prevent the destruction of the entire settlement, Spartan Edward Buck allowed Leonidas to contact the Guardian to notify it of the colony's surrender. After the Guardian accepted the surrender, Alpha-Nine destroyed Leonidas and narrowly escaped Cassidy III without discovering the secrets that planet held.
- Halo: Bad Blood (First appearance)