Carl's Guides

You begin with Arthas, Muradin and two mortar teams. Use the skills of your heroes. Arthas should use holy light to heal and can even soften some things himself using divine shield. Put Muradin in the thick of things and use the clap skill. Begin by heading west. You'll encounter an Undead outpost. Use the mortar teams to fire at the spirit towers and such that defend the base. Don't worry if it seems to take a while, it's better to play it safe on this mission. You'll notice that there is an Altar of Kings in your base if your heroes die, but you can make better progress by avoiding that situation all together.

Once the undead in your way are vanquished you will discover a mercenary camp just west of them, which has some units you can hire to help you. I hired three ogre warriors and two priests. Again, following the path west, you will run into a group of Undead and some spirit towers. Destroy the towers with the mortar teams just like before and try to use your heroes and melee units to eliminate the ground forces. When I killed one of the giant spiders here I found a ring of regeneration, which I gave to Arthas as he cannot use holy light on himself.

With that resistance suppressed you'll find yourself at the first ship: I made it here with 19 minutes left on the clock. Don't fret too much if you don't have any ranged attackers to hit the ship as Muradin can use his storm bolt skill and destroy it in a single hit. Cool, eh?

Now take the south path - note where you could have gone east. You'll encounter a group of some pretty nasty spiders. Keep your units healed and focus your attack on the huge one. Don't neglect that Muradin can use his storm bolt skill to stun enemies. A claws of attack +12 can be found here and I again gave it to Muradin. Destroy the second boat and head a little south and recruit a couple Ogre Magi! They're pretty buff and can cast bloodlust.

Begin heading east, taking out the little groups of minor baddies you encounter and you'll come to a stand of trees you must destroy with your mortar teams. Do this by pressing the 'A' key then selecting a tree and they'll fire upon it. Then, destroy the third boat and proceed to the north. Hire the trappers from the mercenary camp and head toward the dragons to the northeast. Don't let the trappers die, they've got to ensnare the dragons. Start with the big ones and have the other trapper grab the little ones while they're attacking your forces. All out carnage should ensue as your ground/ranged forces obliterate the grounded dragons.

Head to the southeast toward the final two ships. You'll encounter this long path lined with spirit towers. I dealt with this by purchasing an amulet of recall from the goblin merchant here and using Muradin (he had inventory space) to run all the way through them. I then used the amulet to summon my units to him when he was in a safe location. Just make sure all the units you want to teleport are within the circle of effect.