All Challenge Mode guides assume that players have a full understanding of the way the dungeon works in Heroic mode. It is highly recommended that players run the Heroic versions of these dungeons before tackling Challenge Mode. The Heroic Mode run through for Grimrail Depot can be found here.
The strategy below is just one of many ways to complete this challenge. Alternatives are mentioned and even encouraged, so feel free to adjust to fit your composition. Suggested clock times are listed next to each section to help gauge progress.
Rear Train Cars
Forward Train Cars
Trash: Rocketspark and Borka’s Room – 14:30 – 14:00 – Invis Potion
Pull the single Grimrail Laborer on the right and kill him. All of the rest of this trash will be skipped using an Invisibility potion.
Boss: Rocketspark and Borka (Bloodlust # 1) – 14:00 – 12:00
Kill them as you would on Heroic, making sure to kill them as close together as possible. If one of them dies first, try to make sure it is Borka as his damage increases to the tank by quite a bit if left standing.
Trash: Rafters Trash – 12:00 – 10:30
The three Grimrail Bombardier on the way up to the rafters after Rocketspark and Borka can be chain pulled into each other, pulled together or killed one at a time. They cleave and leave a stacking bleed on the tank and will quickly ramp up in damage. When moving them, be aware that they can randomly drop aggro based on their positioning on the ramp.
Trash: Nitrogg Thundertower’s Train Cars – 10:30 – 6:30
These train cars are the longest and most difficult part of this Challenge Mode.
These packs are mostly killed as they are on Heroic, but in the car right before Nitrogg, you can pull two of the packs together to save time. The biggest things to worry about are pulling extra packs on accident and the Shrapnel Blast from the Grom’kar Gunners.
Boss: Nitrogg Thundertower – 6:30 – 4:00
Kill him as you normally would on Heroic. To speed up the kill, try to tank him and the adds next to a turret that can be used to mow them down with shrapnel.
Trash: Skylord Tovra’s Train Car – 4:00 – 2:30
If you are a Death Knight, you will want to use Army on this entire train car. Any other tank class can pull parts of it as a time, or the whole thing if they have enough cooldowns and stuns available. How this car is pulled will vary based on composition and time remaining.
Boss: Skylord Tovra (Bloodlust #2) – 2:30 – 0:00
Kill her as you normally would on Heroic.