This map starts off with a fairly simple main quest: conquer two forts, one to the north and one to the south. As you will soon discover, though, it's not that simple. My suggested strategy here is to take your time and take control of the whole map.
You start with a single town, and not a lot of resources, so get to building the core units. Around you are a bunch of difficult stacks; start off with the easy ones and try to conserve troops (not something Dungeon are known for, I know). Use your hero in battle as much as you can. Go south first and get the item down there, then continue clearing the area while building your town. Take the Ore Pit northwest of your town as soon as your army is strong enough. I'd also keep my secondary hero close to the town to pick up the weekly resources.
East of your town is a Gold Mine and a Blind Maiden so you might want to head there as soon as you can, but the mine is heavily guarded. The path west of that mine leads to the surface but that's not the place to go just yet. North of the gold mine there is a Dungeon Fort which you should take, and to the west of that is an item that boosts your might. East of the fort there is another passage to the surface. Don't use that either yet. Clear out the underground first. It will take time, but you just have to keep building your town, gathering resources and buying creatures. Eventually, you're strong enough to take on all the neutral stacks.
After clearing the underground, I went up using the stairs east of the fort. That takes you to Yellow player's territory. There is a hero and town with pretty good defences there, so be ready. If you're lucky, you can catch the hero outside the town. If not, well … it'll be harder. Anyway, once you take the town, you will gain control of another Gold Mine and Ore Pit, so resources are really starting to mound up. Once you get that town built, you can really get some troops behind your cause.
Get reinforcements by caravan and then proceed south from your new town (of course, make sure you build it). Pretty soon, you will see a Haven fort. If you already beat the main enemy army, this should be easy. Weirdly, this is not your quest target (those are to the west), but take it anyway; you need to keep building your strength. To the west of this fort is an area with several garrisons and a heavily fortified town. Stay away from that town (don't worry, nobody comes out to attack you) and clear the area instead, picking up resources and items, as well as making sure both of your main heroes are boosted to the maximum level. You can take the garrisons; this will make it easier to travel.
Also, this is a good time to send one of your heroes up the stairs just south of (and above) your starting town, the one west of the gold mine down there. Once you have gone up those stairs, you will find two Sawmills and some resources.. North of you is a garrison, and through that you can see an area blocked by wizardly magic. Go around it by heading east, then north, then west. Take that Academy town. Its creatures aren't much good to you at this point, but the spells and extra gold can't hurt. Start building it, though; you'll need the troops later.
Now head north and northwest. You'll find some useful trinkets and resources on the way. Quite soon you'll find a wall. A long, huge “Great wall of China” type wall, ensuring that you can't reach the target fort. Oh well, head back south, follow the road to the south east of your Academy town and presto! You'll find one more town. Take it and you have two. Now it makes sense to have Academy creatures building up. Build the towns, fortify and build up armies of creatures. I'll tell you why later.
Okay, so you have taken the eastern Haven town, the two Academy towns and you're almost completely dominating the map … where the frak is the road to the forts? Here's a clue: look to the east of the southern Academy town. There is an underground passage, take it when you're ready. When you're in the underground, head west and you'll see that you have arrived in a familiar place; those areas in the underground that were unaccessible earlier. There is even a Bloodforge there, but it's heavily guarded and you don't really need it at this point; you can just trade for the resources if you need any.
Keep going west, find the staircase and go up (before you do, though, there is a fort just north of those stairs, you could take that just for the fun of it). Go west and there's the Academy fort, see? Yay! Take it, it should be a snap at this point. There are also a couple of Crystal Caverns nearby, which you should flag. The fort can be rebuilt and use for summoning reinforcements via caravan before you continue.
How to find the northern (Haven) fort? I know this is hard to find, so look at your northern Academy town. Just northwest of it there is a Blackfang Watchtower which stands on a hill. At the bottom of that hill, on the western side, is a well-hidden entrance. There it is. Now you know where to go. Once you've gone down those stairs, explore the area and head north (flag mines and kill creatures if you want to), and once back on the surface, the fort is to the west. It's an easy fight.
Wait a minute. Did I really have you take the time to control the whole map just for that? When you could have snuck through the enemies' lines and taken those forts easily? Yes. But why? Well, you see, taking those forts was only the first part of your quest. Now begins the second part: to visit the trading posts scattered around the map. Firstly, those are well guarded. Secondly, the enemy heroes could pop up and make your life difficult. But not without their towns (giggle). You can do it the quicker way, but then you really have to be quick about it. My way, you can take your time. Besides, who doesn't like to dominate the maps?
Using my method, I now have three huge armies at my disposal; one Dungeon, one Academy and one Haven. Three armies with which to travel around to the well-guarded trading posts. Let's go, shall we? Just follow the clues on the minimap to see where the trading posts are. Once those are visited, the final quest is given.
Now you must destroy that crusader building near the great wall. Use Malwen to do it. Beware that two enemy heroes will come in from the south. Do not attack them! Do, and the map fails. The point is to let them fight each other; they are the response to the rumours you have spread. Coming to investigate, they will find each other and naturally assume the other to be the enemy.
That's pretty much the end of map 2. See you on the other side.