On the day preceding its official discharge, million units of Halo 3 were in retail outlets. Corona 3 netted US$300 million in its first week. More than one million individuals played Halo 3 on Xbox Live in the initial twenty hours. To date, Halo 3 has sold in overabundance of million duplicates, making it the fifth top of the line Xbox 360 round ever, the second smash hit diversion in the Halocfranchise, the top of the line Xbox 360 selective title and the top of the line first individual shooter on the console outside of the Call of Duty recreations. The amusement was additionally the top of the line computer game of 2007 in the . By and large, the amusement was exceptionally generally welcomed by pundits, with the Forge and multiplayerofferings singled out as solid components; however a few analysts censured single-player viewpoints, particularly the plot and battle design. A prequel to the diversion, Halo 3: ODST, was discharged worldwide on September 22, 2009. A continuation, Halo 4, discharged on November 6, 2012, was created by 343 Industries and earned $220 million on its dispatch day. Halo 3 was rereleased as part of Halo: The Master Chief Collection for the Xbox One on November 11, 2014.
Chief makes contact with Infinity and helps repel the Didact's attack. Chief and Cortana recommend attacking the Didact while he is vulnerable, but Infinity captain Del Rio orders them to destroy the gravity well so their ship can escape.  In the process, Chief is contacted by a Forerunner known as the Librarian—the wife of the Didact, as well as ancient humanity's protector.   She explains that the Forerunners were divided on how best to combat the Flood. After failing to discover a way to immunize biological beings from the parasite, the Didact used a device called the Composer to convert the warriors under his command into mechanical Promethean Knights immune to infection. Requiring more soldiers, the Didact forcibly converted captured humans into Prometheans, before being stopped and imprisoned by the Librarian.  The Librarian, who has guided humanity's development, accelerates the Chief's evolution; this grants him immunity to the Composer.