DM-3-1123

DM-3-1123 was a habitable planetary system.

The Forerunners populated the world of DM-3-1123 b in DM-3-1123, but it was eventually attacked by the Flood. While a Forerunner naval group engaged a Flood fleet of 149 non-military vessels in the system, the Flood landed on DM-3-1123 b and infested it, and the Forerunner fleet was forced to bombard the planet to cauterize the Flood's spread.

Trivia

 * The system's name is possibly another 7 reference: 1+1+2+3=7
 * Less than 1.5 million of the 226,911,000,000 residents were saved.