From Halopedia, the Halo wiki
The Oracle is the seventh campaign level of Halo 2, where the player plays as Thel 'Vadamee. Starting directly after Thel 'Vadamee lands the Banshee he was flying in the previous level, the opening cutscene has Rtas 'Vadumee comment on smelling a familiar stench. There are again Special Operations Sangheili and Unggoy as allies and sometimes, an Unggoy Ultra is deployed to assist the player.
The player goes down an elevator and up to the top of the gas mine to cut three cables. They then must backtrack to the hangar of the previous structure, complete with another Banshee-flying section, where the Arbiter engages in combat with the Heretic Leader to prevent him escaping Threshold in a Kai-pattern Seraph. In the cutscene directly before the fight, it is shown that 343 Guilty Spark had survived the destruction of Installation 04 and was responsible for the "heresy" through his teachings.
A door slides open. Two Special Operations Sangheili cover the entrance with plasma rifles while Special Operations Unggoy file in. The Sangheili cautiously advance, followed by Rtas 'Vadumee and Thel 'Vadamee (who is armed with whatever weapon he had at the end of the previous level). Rtas 'Vadumee pauses and sniffs the air.
The assault team proceeds through a small room, where a large tank containing some small, floating, fleshy lifeforms can be seen. The team approaches a doorway, and through the transparent floor of the next room below, they can see the shadows of Heretics and strange creatures battling. Eventually, all of the Heretics are killed. The victorious creatures have familiar screams...
The creatures all leave through another doorway.
The team moves into a laboratory, strewn with deformed corpses.
A floating orb enters the room, and the image of the Heretic Leader appears in the air.
The Unggoy fires on the image, which quickly becomes apparent as a hologram and nothing more.
The Heretic Leader vanishes. Moments later, tiny bulbous creatures start to appear.
The team battles the oncoming Pod infectors. Unless the combat form corpses are destroyed, the Flood begin reanimating them.
The Flood assault subsides, and a doorway opens out of the labs.
The Arbiter and the Special Operations team exit the lab, and step out onto a massive elevator platform. Flood and Sentinels are battling each other all around.
'Vadamee and the survivors ride the elevator down to the lower levels of the labs, fighting multiple waves of Flood and Sentinels along the way. They finally reach the bottom and enter a hallway strewn with corpses.
The team is attacked by multiple waves of Flood and Heretics. Finally, a door opens and a group of Heretics enter the chamber. The Arbiter and any surviving Special Operations troops eliminate the Heretics and escape the chamber through the door.
Vadamee manages to press outside to the exterior of the station. He sees Flood battling more Heretics, and a friendly Phantom swoops in to provide reinforcements and covering fire.
If all four allies (2 Unggoy and 2 Sangheili) from the beginning of the mission survive with the player up until this point, the next line will not be said in gameplay, and no reinforcements will be dropped off:
'Vadamee and his troops advance into the heart of the installation, fighting past Heretics and Sentinels along the way. Inside the facility, they see the Heretic Leader fleeing.
Sesa 'Refumee takes cover behind a shielded door before 'Vadamee can catch him.
'Vadamee notices a hologram of the station, and watches it thoughtfully.
In the Anniversary version, 'Vadumee can briefly be seen nodding at his troops to do it.
If the player has an energy sword already:
If the player does not have an energy sword:
If 'Vadamee follows the Commander and his troops outside, he can see them board the Phantom through its gravity lift.
Thel heads up a winding ramp towards an elevator. He battles Flood and Sentinels along the way. Eventually, he reaches the elevator and activates it.
Hey, Watch This!
'Vadamee rides the elevator to the upper level where the cable is located. Flood and Sentinels are fighting all around him.
If the player spends too much time fighting:
After cutting the first cable:
After cutting the second cable:
'Vadamee cuts the final cable, and the entire station groans with the stress. All the Flood and Sentinels present stop their fighting and look upward towards the cable. The top of the station tears away, and it plummets into the atmosphere. The remaining Sentinels and Flood, if any, are swept out into the sky.
Thel 'Vadamee drops back down into the station, fights through more Flood, as well as a group of Heretics in the doorway where the Heretic Leader once stood.
'Vadamee eventually clears the room, wiping out the Heretic Leader's rearguard and takes an elevator down to what looks like the main power generator for the station.
'Vadamee continues to chase the Heretic Leader. A lance of Heretics, including a sword-wielding Heretic Sangheili charge at him.
'Vadamee kills the Heretics and heads through the door.
The Heretic Leader gets into a Banshee and takes off. The Arbiter fires at the Heretic Leader's Banshee as it flies away, then dodges as the Banshee fires at him in return. The Heretic Leader's Banshee flies away. The Arbiter then dashes out, and gets inside another Banshee and pursues the Heretic Leader.
The Heretic Leader flees under Carbine fire from the pursuing Arbiter. He returns fire with his Plasma Rifle, then runs outside the station, where he boards a Banshee and takes off. The Arbiter runs outside and fires at the Leader's Banshee. The Heretic Leader turns his Banshee around, and 'Vadamee's eyes widen in alarm. The Arbiter barrel rolls behind a parked Banshee just in time to avoid a barrage of plasma fire from the Heretic Leader. He returns fire with his Carbine, and the Heretic Leader's Banshee soon flees. The Arbiter gets into the parked Banshee and takes off in pursuit.
The Arbiter's Banshee flies through the storm.
The Arbiter's Banshee approaches the platform where the Heretic Leader landed.
The Arbiter's Banshee tries to land on the platform, but fails and crashes into it instead. The Arbiter holds on to the edge of the platform, raises himself up, and goes inside.
The Arbiter's Banshee tries to land on the platform, but fails and crashes into it instead. The Arbiter is seen soon after climbing up to the edge of the platform and is heard grunting in frustration from the crash, before he raises himself up as he surveys the plummeting scenery behind him and runs inside, fully intent on catching the Heretic Leader.
Dead Or Alive...Actually, Just Dead
'Vadamee fights through the first portion of the station, engaging large numbers of Flood forms as well as retreating Heretics and the station's few remaining Sentinels. He makes it into an open conveyor room where a large number of Heretics make a last stand against encroaching Flood forces to buy their leader time to escape. 'Vadamee breaks through this last line of defense and makes it to the hangar.
The Arbiter catches the Heretic Leader as he is about to board the Seraph. 'Vadamee points his weapon at the Heretic Leader in confrontation.
The Heretic Leader stops in his track, (grunts in the Anniversary version as if he recognizes whose voice he heard), before he turns to face the Arbiter.
A familiar humming is heard. The Arbiter looks up and sees 343 Guilty Spark descending from above.
While 'Vadamee stares in surprise at the Monitor, any questions are cut off as the Heretic Leader suddenly reaches for his twin Plasma Rifles and opens fire on 'Vadamee (who returns fire in the Anniversary version.) 'Vadamee falls back, taking cover while his shield generator recharges. As he does so, the Heretic Leader floats back toward the Seraph and pulls out two holodrones.
The Heretic Leader releases the drones, which become copies of him. They turn to look at the Arbiter.
'Vadamee battles the Heretic Leader and his holo-drones.
On Heroic and Legendary, whenever the Arbiter destroys the holo-drones, 'Refumee will retreat to one of the hangar's upper air vents and hide for a while before releasing two more holo-drones and emerging to resume the battle.
While in hiding, 'Refumee will speak to Thel 'Vadamee.
On Legendary only:
During the fight 'Refumee continues to taunt the Arbiter:
If Sesa 'Refumee kills the player, he may say one of the following lines:
343 Guilty Spark will also talk to Thel 'Vadamee throughout the battle.
If the player continues the fight long enough:
If the fight is drawn out even longer:
The Arbiter finally kills the Heretic Leader.
'Vadamee has killed the Heretic Leader and is dragging his corpse to the hangar door.
343 Guilty Spark is snatched by an unseen force and pulled away. He is dragged through the air, directly to the top of the Fist of Rukt, the gravity hammer of Tartarus. Tartarus, standing beneath a Phantom, pulls 343 Guilty Spark off the end of his hammer.
Tartarus casually tosses 343 Guilty Spark into the Gravity Lift.
Fades to black.
Halo 2: Anniversary