Raid at Codisfold

The Raid at Codisfold was a battle that took place during the War of Beginnings in the rings around Codisfold, a Sangheili colony. During the raid, the Sangheili managed to infiltrate the Anodyne Spirit, killing thousands of San'Shyuum. In response, Codisfold was ravaged and millions of Sangheili on the planet were killed.

Background
As the War of Beginnings raged on, the Anodyne Spirit, the San'Shyuum's Forerunner Dreadnought, seemed an insurmountable obstacle for the Sangheili. Despite outmatching the San'Shyuum themselves in combat, their Dreadnought allowed their enemy to devastate Sangheili colonies one by one. Eventually, the Sangheili came up with a plan to defeat the vessel. They would sacrifice their colony of Codisfold, hiding dozens of ship-boring machines in the rings around the planet, hoping that the San'Shyuum would bring their Dreadnought close enough to board.

The raid
When the San'Shyuum arrived to destroy Codisfold, the ship-boring machines launched, carrying skilled Sangheili infiltration teams. The teams secretly snuck onto the Dreadnought, compromising several of the vessel's critical systems and slaying thousands of San'Shyuum. While taken by surprise, the San'Shyuum eventually managed to kill all of the Sangheili intruders.

Following the incursion, the San'Shyuum attacked Codisfold, killing millions of Sangheili residents.

Aftermath
Despite the massive loss of Sangheili life, the raid forced the San'Shyuum to acknowledge their vulnerability and the unrest it caused among them would help pave the way toward a truce between the two species, and ultimately the formation of the Covenant. While many of the surviving San'Shyuum began to consider a cease-fire as a result of this event, Pervading Stone, the leader of the Keepers of the Dawn, simply demanded more Sangheili blood. Breaking Shadow and Ushering Dusk—both members of the Keepers of the Dawn as well—lobbied for peace. Some other San'Shyuum spoke up against Pervading Stone, but they were only silenced or eliminated when necessary. Around this time, Stone secretly ordered the assassination of Dusk, to remove him as an obstacle.

List of appearances

 * Halo: Shadows of Reach
 * Sacrifice