From Halopedia, the Halo wiki
Ethan Graves was a human of the UNSC Marine Corps serving as an Orbital Drop Shock Trooper. Born in around 2515 on the Jovian Habitats in the Sol system, he specialized in tactics and command. Graves was the leader of Fireteam Raven, an elite team of ODSTs attached to UNSC Pillar of Autumn during the Battle of Installation 04.
Graves was born in around 2515 in the Jovian habitat clusters on Io. During his childhood, Graves' father would often speak of Jupiter as the true unsung hero of humanity due to the gas giant's gravitational influence on rogue asteroids, comets and other incursions sparing Earth from destruction long ago.
Ethan joined the UNSC Marine Corps as much to get away from a life working the factories and mines as to fight the Insurrection, but his sharp intellect and decisiveness made him a natural leader. He rose quickly through the ranks, always leading from the front, earning him the admiration of his officers and the respect of his squad members. When the Covenant attacked, Graves immediately requested admission to the ODST, he knew that now, more than ever before, Earth was under threat from beyond and it was his Jovian duty to defend her.
Battle of Installation 04
By August 2552, Ethan was the squad leader of the elite ODST team, Fireteam Raven. Raven were present aboard the Halcyon-class light cruiser UNSC Pillar of Autumn for Operation: RED FLAG and the Fall of Reach, as well as the ship's subsequent escape from the battle on August 30. On September 19, the cruiser arrived in the Soell system at Installation 04 and the crew was brought back online. Raven were among the soldiers ordered by Major Antonio Silva to defend the ship from Covenant boarding actions, and were succesfully able to fend off waves of Sangheili, Kig-Yar and Unggoy before proceeding to perform a spacewalk and man the vessel's M910 Rampart point defense network, at the request of the AI Wellsley.
However, the squad would eventually retreat back to the cruiser's SOEIV drop bays and abandon ship, along with the rest of the ship's crew complement. Graves and his squad would land on Installation 04 accompanied by a mobile uplink to Wellsley, and begin the journey to reunite with allied forces on the ringworld. Roughly 28 hours later, Raven would link up with an armored convoy led by Lieutenant Melissa McKay, and man an M12B Warthog during the Raid on the Pillar of Autumn. Graves would later return to Alpha Base in time for the Covenant attack there, and join the camp's defense.
During the defense of Alpha Base, Graves and Raven were recalled to the canyons near the Halo's control room to defend against an emerging threat - the Flood. The team was inserted via Falcon to clear the way for an important mission being undertaken by John-117. Graves would help fight off numerous waves of Covenant and Flood forces, but eventually extract out of the canyon once the Spartan's mission was complete there. However, the team's Falcon was shot down by a Type-26 Wraith, and crashed elsewhere on the ring near a Forerunner structure. The team would make their way inside the structure for cover from the battling Covenant and Flood while they awaited extraction, and eventually were able to take down several Flood Juggernauts before their D77-TC Pelican was able to pull them out.
With Halo's purpose now clear and the situation deteriorating rapidly, the Master Chief was left with no choice but to destroy the ring. To facilitate the ring's destruction, Graves and his squad joined a last-ditch UNSC attempt to hold off Covenant forces descending on the crash site of the Pillar of Autumn. The squad were deployed in a Warthog to fight off Covenant and Flood ground forces. The squad would eventually take down a Type-47B Scarab and masses of Flood and Covenant, but ultimately die along with all other personnel on the ring during the explosion caused by the detonation of the nuclear fusion reactors of the Pillar of Autumn.
List of appearances