A new unit joins you, the crypt fiend. These guys are capable of using the web skill to pull flying units from the air. They're pretty damn useful, like that, and they can auto-cast it which makes them even more useful. You'll need to construct a base first and foremost, and the elven base to the southeast is a good place to do so. Destroy it, making sure to have the crypt fiends get within webbing range of the flying units here. With them downed you should have no trouble. Begin constructing your base and check to the east. You'll find a goblin merchant. This one makes zeppelins, sappers and allows you to use the reveal ability. It's basically yours since it's so close to your base. You just must have Arthas in range of it to build the units/use the ability.

As you may have guessed you will want to keep some crypt fiends in your base to take down any flying units that come, and they surely will, as there is no bridge to get to your base. With that in mind decent coverage from your spirit towers should be applied. That way there's no real holes in your defense and the woodcutting ghouls/webbing crypt fiends can bring them down and finish them off while Arthas is busy elsewhere. Build an extra meat wagon or two, on top of what you started with and make a well balanced attack force for Arthas to lead. Load the troops into the zeppelins and send them across the river to the east. Focus the meat wagons' fire on the defensive tower while the ground troops swarm everything in sight. If you encounter a dragon hawk make that a top priority kill though, they're pretty powerful. This base is not too well defended and it is even one of the three bases with the moon crystals. Destroy the Altar here and order Arthas to collect the first moon crystal. You will find here two useful things.

The first is a gold mine you can/should haunt as the first one didn't have all that much in it to begin with. Don't forget to put a spirit tower or two near the gold mine to protect it as it's on its own piece of land. Second, you will find a waygate here which you can use to teleport your units across the river to the northwest.

First, replenish any forces you lost and maybe add an additional meat wagon or two. Then head through the waygate. A small defensive force is here to greet you and, when they're defeated, you can move on to conquer the base to the south. On this piece of land you can find two waygates. The first one you come across leads outside the northeastern base which is protecting another moon crystal. The second waygate leads to the northwestern base. I chose to go through the first (red) waygate and take that base down first, as it appeared to be the most threatening. There's nothing too complicated here. The battle goes like all the others so far on this map. Be sure to bring some crypt fiends, and you'll do fine. With the second altar destroyed you now posess the partial key of the three moons.

Head back through the red waygate and prepare a final assault group to take the final crystal. The battle will begin right when you go through the last (blue) waygate. I decided to blow the rest of my resources on sappers because I'd never got to use them before. I used them to suicide bomb the final altar. Send your main force through first to distract the units there then send the sappers one by one into the altar. Have Arthas grab the moon crystal and you don't even need to finish off the final base. But now you must get Arthas to the gates. I chose to land my forces just northeast of the first blue waygate. Use the goblin laboratory's reveal ability to make sure it's safe. Bring enough ghouls to create a diversion for Arthas to make it to the gate safely. You will want to land your forces quickly when they're on the other side as there are heavy anti-air defenses here. When landed charge your forces for the gate and have Arthas step on the circle of power.