Orbital Drop Shock Troopers are a highly regarded division of UNSC forces, known colloquially as "Helljumpers". ODSTs are the best of the best in the UNSC military's infantry, excluding the Spartan supersoldier program. These Marines are chosen for high-risk missions, such as opening up new landing zones in hostile territory, and are often inserted from orbit in drop pods. ODSTs are often extremely cocky because of their elite status within the UNSC, and the status their reputation has brought. They, along with their superiors, look down upon any Navy personnel who accompany them on missions, and in the Halo novels are at odds with the Spartans. The ODST's do not view their super-solider brethren as human and are extremely antagonistic toward them as individuals and the SPARTAN program as a whole, although the Spartans (who tend to be extremely focused on their mission) do not usually reciprocate. The one exception to this is an occasion when Spartan John-117 got into a fight with four soldiers aboard a UNSC warship.
Role on Alpha Halo
Although the ODST's did not appear in their signature uniforms until Halo 2, they did carry out operations on Alpha Halo in parallel to the Master Chief and other Marine regulars. Upon landing on Installation 04, they quickly took a strategic point from the Covenant that was set on top of a low mesa. From there they conducted operations to both repel and attack the surrounding Covenant forces. They did in fact commandeer the Covenant vessel Truth and Reconciliation, and were going to use it to escape the structure. However, one of the officers, realizing that going to Earth with Flood still aboard would jeopardize humanity, sabotaged the ship, causing it to crash and kill everyone on board.
Role on Delta Halo
ODSTs appear prominently in a mid-game Halo 2 mission, where they perform a combat drop with pods launched from the UNSC In Amber Clad to secure a landing zone on the ring's surface. They are accompanied by the Master Chief, who leaves them behind in pursuit of the Prophet of Regret shortly after reinforcements begin to arrive.
ODST's are featured heavily in the Halo 3 promotional short films by Neill Blomkamp, who was signed on to direct the full-length motion picture adaptation of the Halo franchise that later fell apart when a standoff between FOX and Universal resulted in a collapse of funding. The shorts depict UNSC marines, including ODSTs, on missions prior to the Master Chief's return to Earth. They portray the soldiers in acts preparing for the rendezvous with SPARTAN-117, and also serve to display the front line warfare experienced by the UNSC personnel on the ground. Some variations can be observed on the armour of the ODST's in the films. Instead of the familiar metallic black, their helmets' visors are a dark, almost red-black color. Also, in one shot, a soldier's blood type can be seen displayed on his right shoulder guard. This is likely used to make wound treatment and any needed blood transfusions easier, especially when dealing with conditions which surpass the use of biofoam (a substance injected into a wound to seal it and encourage healing).
Battle of the Ark
A team of ODSTs were deployed onto the surface of the Ark along with the Master Chief in order to secure a safe landing zone for the UNSC Forward Unto Dawn, which was barely holding out against the Covenant fleet above. Along the way other ODST drop pods were encountered, but their occupants were killed, either by impact or the enemies awaiting their arrival. Upon successful landing, the Dawn unloaded a group of tanks and Marines to further assist the Master Chief, and the ODSTs were extracted by Pelican.
Halo 3: ODST
Shock Troopers are prominent as the main playable characters in Halo 3: ODST, a "midquel" taking place during the latter half of Halo 2, in the city of New Mombasa, after a botched landing. The primary protagonist, the first playable Human character in the Halo franchise who is not a Spartan, is an ODST known only as " the Rookie", The player also gets to play the perspective of four other Helljumpers, Buck, Dutch, Mickey, and Romeo, through flashback sequences.