Delta Sector 5 - The Delta Complex is the most advanced research facility on Mars. The complex is divided in the three main sectors, each serving unique purposes and one smaller sector that houses the main portal. Access can only be gained through the monorail or CPU Complex.

Betruger's voice come over the announcing system: "You are too late! Hell no longer needs that portal to enter this world. The invasion you saw was only the first wave. The Hell Gate it capable of sending millions of my children into your world. Soon, the fleet from Earth will be here, and with their ship, we will being this Hell to Earth!"

Your first mission is to the destroy the Hell Portal. It will turn out that you'll need to do some other things first...

You're in the main portal room in Delta Labs 5. Straight ahead is 2 30 health packs, a machine gun, 2 clips, a pistol and bullets. Pick them up. Don't bother with the door; it is locked. Keep going straight, down the stairs, and you'll notice a grate in the floor is missing. Jump down and follow the ducting. You'll pick up a flashlight here as well. As you go, you'll notice some armor shards and a pack of grenades in the duct. The grenades will come in handy in a minute. Further on, there are also 2 clips off to the right. Since you lost all your weapons and ammo coming back through the Hell Gate, pick up everything.

Finally you'll come to an opening in the ducting heading up into a passage. You'll hear a chain gun-soldier coming from behind you and then pause. Arm the grenades, and wait until he stops. Then stand up and throw 2 grenades fast, one right after the other. Climb up and pick up the chain gun. Go backwards (from where you heard him come from) and go through the door. You'll see a whip-solider coming at you. Kill him, and keep going to the left. At the end (its a dead end), pick up the chainsaw, the 50 armor, and the ammo belt. Go back to where you came out of the duct, and keep going. Pick up the ammo elt near the bay door, and then use the panel to the right of the door to open it.

Get the machine gun ready, because there will be a hallway off to your right that twenty-eight spiders will come from 1-2 at a time. One way to handle it was to stand back in the bay door area and shoot them as they come into the light, but if you miss, they jump on you. Kill all the spiders and and proceed down the hallway (don't go straight, it just dead ends at the bridge that was destroyed in Delta Labs 4). Arm the soul cube (it will be ready, since it activates every 5 kills). A soldier will teleport in, kill him with the soul cube. It will also fill up your life. No arm the chain gun and keep walking. A panel will fall open to your right, but a soldier will spawn behind you. You can kill him with the chain gun without taking any damage. Inside the panel is a plasma gun, 2 plasma canisters, 2 clips, a 15 health pack and a pack of hand grenades. Keep going down the hallway into the elevator shaft, turn right, and start climbing the ladder.

At the top, there is 50 armor on your left. Grab it, turn right, and duck into the duct. Follow it until you hear the footsteps of the chain gun soldier. Look down and you'll see him going down a set of steps. Toss a grenade down to soften him up, jump down, and finish him with the plasma gun. Walk down the stairs. A whip-soldier will come around the crates. Kill him , and grab the shotgun and 32 clips from outside the crates. Inside, there are 2 boxes of shells and another clip. There is an arch-vile next, so arm your favorite arch-vile-killing weapon. 3 blasts from the shotgun at close range works well.

Proceed around the crates and through the warehouse. A bay door will open at the end with an arch-vile. An easy way to kill him is to run up and shoot him three times with the shotgun (don't forget to avoid his flame attack!) A whip-soldier will now be running at you from behind, so spin around and kill him (duck to avoid the tentacle attack). There is some plasma canisters and armor shards in the bay where the arch-vile was. Proceed out of the bay, up the stairs (on the right). Another arch-vile will show up from the door on the right at the end of the catwalk. If you're hurting on health, you can use the soul cube, or save it for the whip-soldier that will be coming form behind again. Kill both, and proceed through the door.

Use the lift to go down to the first floor. Kill the chain gun-soldier that runs up. Grab his chain gun and go through the door. You'll hear a revenant at the top of the stairs. 2 shotgun blasts will kill him. There's nothing useful in this room, so go up the stairs, turn left and go through the door. Again, there is nothing useful here (even the Emergency Medical Station has 0 health in it), so use the elevator to go up to Floor 2 - Delta Authority.

Exit the elevator, and go around behind it to the Delta Authority entrance. Go through the door and you'll see Elliot Swann sitting on the floor, injured. Take his PDA (you'll need the security clearance). He explains that he's injured, but that Sarge is now be turned, and he doesn't know how long he's "been working against us." He also explains that you've got to destroy the portal before the fleet from Earth arrives. Your mission has changed: Use Swann's PDA to gain access to the CPU Complex.

Go straight, pass the desk, and turn left and go through the door. You'll see an open panel on the floor. Jump down, and go through the duct. Go all the way until you see a ladder. Climb up, but there's no where to go. The duct you just came out of had two levels, and you came from the lowest one. Jump back in and follow the middle duct. When you can stand up again, you'll see a rack with 4 armor shards, 2 plasma canisters, 50 armor, 30 health and 2 boxes of shells. Gear up and make sure all your weapons are reloaded. Turn around, and use the panel to extend the service ladder which will take you down the the lobby you last saw in Delta Labs 4.

Climb down the ladder into the lobby. An arch-vile will appear ahead of you down the stairs. He'll spawn a whip-soldier to your left near the entrance to the CPU Complex. As soon as you kill the arch-vile, another one will spawn to the right, along with another whip-soldier. The sooner you kill the arch-viles the better, since they can spawn monsters all day. There is 30 health and a clip to the right of where you climbed down, and there is 50 armor hidden in the tentacle area straight ahead down the stairs. When you're done fighting and grabbing everything, go back up the stairs and use the panel to the right of the door to get into the CPU Complex.

Inside, turn right, then left, then left again. There will be a revenant. Kill him, and you can pick up the 30 health to your left, and the 50 armor and 2 clips to the right. If you need chain gun ammo, there is a hidden ammo belt if you jump over the railing and walk along the service area at the end.

For some id software humor, turn right just before you go through the bay door and download the "Pointers to remember when opening sacrificial portals". When you're ready, open the bay door and Exit Delta Labs to move on to Central Processing.