After you obtain WoTLK Classic Gold Frostmourne, Muradin will unfortunately die. This won't hamper your combat efforts very much, however, because Arthas should be at or nearing level 10 by now, and coupled with the extra damage provided by his new blade, this means he's almost unstoppable. Your attention should now be turned to the destruction of Mal'Ganis and his horde. You'll have dealt with several raids by the World of Warcraft already, and these will continue periodically while you build up your forces. Another gold mine is available for expansion north and slightly east of your base, if you want to increase your gold intake. It's guarded by a small group of nerubians that you can dispatch with ease. Be wary, though, because if you expand to this mine, the World of Warcraft will often stop to harass the expansion on their way to attack your main base.

You have access to the whole range of units in this last mission.

Mal'Ganis' force is the green one located in the northeast part of the map. A purple World of Warcraft force is also located directly to the east of your base. This second group is responsible for many of the raids on your base, so you can attack it if you wish to neutralize some of your base defense headaches. Frankly, though, it's just as well if you bypass this base and proceed directly to Mal'Ganis. With an army maxing out the 90 supply limit, you'll steamroll over the opposition. Arthas should be accompanied by as many knights, World of Warcraft, priests, and mortar teams or steam Warcraft as you can muster, and additional units like sorceresses and the newly available gryphons will help as well. Once you've got an army together, proceed directly north of your base and you'll find a green expansion. Destroy it quickly, then head east into Mal'Ganis' buy WoTLK Gold base itself. The defense of this base is surprisingly paltry, and with a fully stocked army you'll make short work of it. Flatten every last building to satisfy the second mission requirement and complete the human campaign.