In this chapter, Titus helps escort Inquisitor Drogan to safety, and holds off a huge Ork force single-handedly, kicking ass and not even bothering to take names.
This chapter is pretty long, so hold on and get ready!
Run up the rubble and receive a new objective: "Rendezvous with the Inquisitor". Your squad will have a short conversation about Ork strategy; afterwards, continue forward. When you go down a steep drop, immediately turn around pick up the Servo Skull (Medicae Station Ventris 4/5). Turn around again and walk into the next cutscene.
When the cutscene finishes, there should be a Support Pod right in front of you. Switch out your Melta for a Lascannon if you wish. Walk forward, and you'll get another cutscene introducing you to the mighty Shoota Nob. In this fight, the Nobz attack from a distance and don't send flunkies, meaning that if they away your health, you can't get it back. Kill them before they get the chance.
Video: (NOTE: Chapter 8 begins at 6:44) 500px|left|
Continue forward into the blood-strewn hallway. On your immediate right is a Servo Skull (Inquisitor Drogan 3/5). Head right out of that room and go up the stairs. Drop down and continue forward until you see more Orks in need of slaughtering. I assume you would be more than happy to oblige. Having done so, head up the stairs directly across from where you came in and hit another checkpoint.
Pick up more ammo and continue upstairs, where you'll have to fight again. Save your Lascannon for the Shoota Nob, and take out the rest with your other weapons. Continue your trail of carnage forward until you reach some more ruins. Go left and head downstairs, getting rid of the Slugga Nobz coming up. Continue killing indescriminately, and make a slight diversion when you're well inside the tunnels. Turn right for another Servo Skull (Worker Nathaniel 1/5), then move forward again, and up.
Move forward again. After a while you'll meet some more Shoota Boyz, so take care of them. Once you're done, head upstairs and reinforcements will arrive directly behind you. Get out your long-range weapons and deal with them. Continue left and across towards where the reinforcements were positioned moments ago. Divert a bit to the right and pick up a Servo Skull (Inquisitor Drogan 4/5). Follow your Objective Marker up the rubble ramp.
Video: (NOTE: the video is mislabeled, and does in fact contain footage from Chapter 8) 500px|left
Continue forward and, after a short conversation, another long-distance fight starts. Do what you do best. Continue forward, and then left. Move forward and hit a checkpoint, and a cutscene.
After the cutscene with Drogan, move forward and hit another checkpoint.
Follow the linear hallway to the next checkpoint.
Move forward, pick up some ammo and run.
Pick up the grenades in front of you, then run down into the arena-like pile of rubble, where some Slugga Boyz are about to line up for the slaughter. Put them out of their misery. Some Shoota Boyz, Rokkit Boyz and Slugga Nobz will also join the fray. Rinse and repeat. Once everyone's dead, a cutscene will play.
Now it's your job to hold off the Ork attack while Drogan and your squadmates make an escape. Kill everyone you see then move up two sets of stairs.
Keep running forward, and grab a Jump Pack from the Support Pod. You'll also get the Thunder Hammer, an extremely powerful melee weapon whose only major drawback is a limited firearm arsenal. Now we're talkin'!
Leap over the barrier in front of you and grab some ammo. Continue marching on.
Move forward, then down, towards the objective marker. Hover over the burning wreckage and pick up the grenades and ammo.
After getting a message from Drogan, storm up the stairs and jump up over the barrier. Move forward towards the objective marker and jump into another arena area. There's a small area to the left of where you came in where you can jump down and pick up another Skull Servo (Workshift 465 4/5). Your objective marker will change, focusing on the Weirdboy spawning enemies. Focus on taking out the Weirdboy before you're overwhelmed. Shooting the Weirdboy won't do much because he has a psyker shield, so you should Ground Pound before following that up with melee attacks.
Once you've killed the Weirdboy, follow the objective marker and drop down. Continue moving forward until you hit another checkpoint.
You'll have to contend with another Rokkit Boy and Shoota Nob-filled battle, but it shouldn't be overly difficult. After you've killed everyone you'll get another message from a Guardsman thanking you for saving them from the Orks. He tells you there are still more Orks to kill in Marsis Plaza. Well you've come this far, haven't you? Make your way upstairs.
Jump over the barrier and Sidonus will contact you again, saying you are nearing the Imperial Guard bastion. Take out all the Orks and keep moving upstairs.
You'll have to fight another Weirdboy. Once again, ignore the other enemies and go straight for the Weirdboy, using the Jump Pack to subdue him. Once he's dead, the force field blocking your path will disappear. Go through it, and your Jump Pack will conveniently run out of fuel. Continue forward.
Run forward and you'll get a message from 2nd Lieutenant Mira ordering her soldiers to hold the line from an Ork attack. Run forward and talk to her, and she will help you get to Kalkys as fast as she can. Approach the Valkyrie in the middle of the battlefield to end the chapter. Finally!