Warcraft 3 Frozen Throne Walkthrough for Undead Scourge:
Chapter 7 Part 1: Into the Shadow Web Caverns
Main Quest: The Old Kingdom
Use your Meat Wagon to fire on the explosive barrels across the dropped floor. This will trigger an explosion allowing your army passage. Slaughter the Dwarves, ensuring them no pints for the evening. Stepping on the glowing switch will open the door. You will likely lose your ghouls in this room if you don't attack the siege engine with Anub'arak and Arthas alone, as its flames damage them so quickly it's hard to hit the ghouls with death coil. It really doesn't matter, as Arthas and Anub'arak could do this alone. Anub'arak can summon his beetles from the corpses in the meat wagon, as well.
Optional Quest: Gold Stashes
If you break open the barrels in this room, you'll receive the first of five gold stashes in this level. Hit the barrels with one of your units (they can't be hurt by the explosions) and proceed east. There are a number of spiders and egg sacks here, and they should all be killed because Anub'arak can use the experience. The next switch is behind some boulders in the northeastern corner, and there is another stash of gold in the southeast. Proceed through the rolling stone door.
When you reach the "dead end" commentary scene, break open the barrels to find a tome of intelligence. I chose to give this to Anub'arak because his skills are quite useful and he has a lack of mana. Again, look for the switch to the rolling stone door. This time it's under the rock chunks blocking the door. Break open all the barrels in the next room. There is a third stash of gold in here. Breaking down the Ancient Door to the east will also lead to a spiked collar. This is not a very good item but I suggest you carry it with Arthas because it can come in handy on a later mission to get a better item! Flip the switch before you step on the floor plate to deactivate the spike trap. The other switch here brings out a pair of spiders for you to fight, and will come in handy for gaining experience with Anub'arak. Cracking open the Vault to the north will trigger the dwarves to attack you. Get the orb of frost for Anub'arak to grant him a ranged attack against air, and slowing attacks which are invaluable.
The next room has a load of explosive barrels. If you don't have any ranged fighters left there's a barrel in the corner that a melee fighter can hit. It will kill all the dwarves as the barrels go up. If you have room, there's a healing salve hidden in one of the barrels to the north. Otherwise, go south. Kill the dwarves again. Note that killing dwarves with explosives doesn't seem to give experience so avoid it when you can. You'll eventually reach the point where the bridge as blown, which means you're very close to the end. When you reach the fountain of restoration, note the gold coins hidden in the waterfall. The next room is where you fight Muradin, who will drop the blood key. You'll have to make a choice as to what to keep here. For me the worst item was Anub'arak's ring of superiority. Have Anub or whoever got the key stand on the circle to complete the chapter.