Rampant
Objective: Find Cortana
After the cut-scene, proceed directly ahead into the bowels of Flood's lair. Fight your way through the first big room, and then pick up the pair of Spikers in front of the first door you pass through.

Through the first door, you'll pass a short corridor, where you'll have to jump down through another door. Time for a big fight.

Enemy soldiers descend down the hill landing right in front of you. Stay at the bottom and kill them as they come down. When you run out of ammo, simply run to the base of the hill -- where you have been slaying enemies in mass -- and collect a new one. Head up the top of the hill when you've finished the first wave.

Another wave of enemies will spawn when you reach the top of the hill. Fall back down the hill, and repeat the same strategy until they stop coming down. Then work your way back up the hill, killing the stragglers. Note: To the left of the hill (assuming you're facing upwards), there's a door outside, where you see a crashed Pelican.

Lying next to this Pelican is a flamethrower, which, if you hold onto it until you get the next one, can be incredibly useful to get through the first section.

As you proceed down the large tunnel at the top of the hill, make sure you have a long ranged weapon. There will be Floods that can shoot spikes from long distance. Use a gun to shoot them off the walls and roofs before proceeding.

Continue down the tunnel, following the blue arrow through the doorway. You will now get a brief reprieve; the next two rooms will have zero enemies.

After passing through another door you'll come into a room where several corpses stand up. Kill them and then scavenge the area for weapons, then head for the tunnel.

The tunnel will end with another hole that you have to drop through, which will lead you into a room filled with Floods. Hang back at the place where you've dropped down, letting them come to you.

Proceed slowly into the room and kill the remaining enemies. Your goal will be to get through the door on the opposite side of the room from where you started (look for the blue arrow).

Pass through the doorway and through the short hallway, until you come to a large room filled with enemies. To your right will be a small hallway, where there is a flame thrower.

Grab the flame thrower and enter the large room, burning all who stand in your way.

When you get to the end of this room you'll be out of ammo for most of your weapons, but that's OK since in the next room, just through the door you've passed through, will be a Covenant Carbine sitting on a rack. First, use your remaining ammo to kill the wave of Flood that will hit you right at the door, and then pick up the Carbine. With the Carbine in hand, shoot the Flood on the upper pathway, and snipe the remaining Flood you can see from the doorway.

After you have cleared out the Flood with the Carbine, ditch the gun, and pick up ranged weapons. Now, with guns in hand, proceed through the room, fighting your way up the various levels of the room. Eventually, when you reach the top, you'll jump across a small chasm and go through a doorway.

Go through the doorway, through the short hallway, and into the reactor room.

Kill all the Flood around the perimeter of the room, and then head out along the fleshy pathway that leads to the room's center. From here, take the path to your right, which branches towards the rest of the room's perimeter. It will be marked by a blue arrow.

Proceed through the non-Flood converted doors and to the computer in the center of the room. Punch your way through the shield, and free Cortana.
----------------------------------------------------------------------------------Nor Hell a Fury…
Now that you have Cortana back, head back into the reactor room, prompting the following objective.

Objective: Destroy the reactor
Get back out to the center of the room and hit the switch on the computer, exposing the reactor's pylons.

Now shoot the three glowing pylons marked by blue arrows. And don't worry about getting close; even a pistol can set them off from a distance.

You will be given a new objective when the reactions are destroyed.
----------------------------------------------------------------------------------Objective: Escape High Charity

After fighting to the other side of the reactor room, Cortana informs you that an explosion has made a new exit. She marks the path way on your HUD with a series of blue arrows. Follow them back through the rooms that you previously fought through, killing as much Flood as you need to. Remember, you're not trying to kill them all; you're trying to kill any who slows you down from getting to the exit.

After you proceed through the areas you previously went through, Cortana will tell you that she has picked up a friendly contact. Run to the blue arrow on your HUD, which turns out to be the Arbiter, complete with a flame thrower.

Now, with the Arbiter leading the way, fight your way to the final blue arrow that Cortana puts up on your HUD. It will lead you to a Pelican that, when you board it, will signal the end of Mission 8.