In 2535, during the Human-Covenant war, following the loss of most of the Outer Colonies, refugees had started flooding the planet and all available space was being used for victory gardens and refugee camps. Vice Admiral Jean Mawikizi resolved to make a stand against the Covenant on Chi Rho, digging in deep within the planet's crust to survive a glassing attack, forcing the Covenant to come down and flush them out man-to-man. Eventually the planet did come under attack.
Chi Rho had conditions very similar to Earth. It is unknown if this is due to terraforming or if it Chi Rho naturally had these conditions.
- The name "Chi Rho" could be another biblical reference in Halo. The Catholic symbol of the letter X and letter P written as a single letter is called chi-rho. The symbol stands for the first two letters of Christ in Greek. It's also the reason Christmas can be abbreviated as Xmas.
- Halo: The Cole Protocol (First appearance)
- Halo: Fractures - Extraordinary Tales from the Halo Canon