Welcome to the main campaign, the story of Ivan.
Here's a little about Ivan: he is a typical leader and strategist - he is skilled in Diplomacy, and you should build that skill further and keep an eye out for creatures who will join you. If you run into some creatures who will join for a price you can't afford, just save up money and come back later. Ivan doesn't have much magic to speak of, but you can get some Light or Prime if you need it. Mostly, though, Ivan is about boosting the strength of his army. Keep that in mind when choosing which items to carry. Build Economy and Leadership. Also, in your town, build the Embassy quickly, to get more creatures joining you. Last thing: remember to appoint Ivan as governor of your town if you're getting governor skills (which you should).
Remember what I said in the Haven walkthrough: the strength of this faction lies in conserving troops, sustaining low losses by having high defense, using healing or resurrection abilities and the like. You can win quite easily if you use those skills correctly.
You start out on level 10, with a slightly built town and some creatures. The mission is to talk to your advisors (as if they haven't spent enough time sitting around that table already); you can start with Anastasya, since she is right next to you. Once you do, a portal is opened north of town. Kente (who can apparently mend bridges simply by having a conversation) is just to the west, so chat with him too. Then clear the area an claim the mines north of your town to get a steady income of wood, ore and gold.
The portal leads to a small area in the Underground, feel free to visit it any time. You get a quest: finding the pieces of an old sword. Another piece lies to the west of your town.
When you have cleared out your area, you should bring some creatures and move through the garrison to the north. Clear the area, flagging mines and visiting boosters. To the north is a gold dragon for you to talk to; he gives you a quest: destroy the evil hydras further north. You need a sizeable army to do that, so you may have to go back home. Also, remember that the Dark Hydra has life drain, so it just keeps on fighting … Do several trips if you need to, there's no rush. I'd take the left stack first, since it's guarding an artifact that gives you +8 defense. Afterwards, talk to the dragons again to complete the quest. There's a chance they'll join you, so check if you can talk to them a third time.
Just to the west is Murazel, ready for a talk. Once you visit her, you get some free creatures and another piece of the sword. North of her is a stack of neutrals you can only reach if you manipulate the bridge; the prize is a purse giving you +250 gold/day, but if you go for it, remember to swap items in the inventory before each fight, since it occupies the same slot as that all-important shield (and you can't recruit more heroes yet to carry the purse for you). Continue moving northwards and near the river you will find your buddy Lasir. Let's go say hi!
Well, that did a lot of good. Darned elves. Well, I guess his tip of a fishing trip may hold something of value anyway. Oh, who's this? Wilhelm? Here? And he says Seamus is willing to admit defeat? Somehow I don't quite believe him …
After you have visited everything in the northern territories, bring a big army, prepare for combat and go through those newly opened doors. Yeah, that marriage deal did sound a little bit too good to be true. Vayaron is the blade Seamus wields here, but if you brought an army worth mentioning, he shouldn't stay in your way for long. Kill him until he dies from it.
After this whole affair, Anastasya joins your cause as a playable hero. She's a pretty strong hero, so give her a decent Haven army (ditch those necro creatures) and you'll have a real second force at your disposal. Visit the Altar of Sylanna on the hilltop; that can get you into the areas blocked by the green seals. Those Stag duchy heroes roaming around are now no longer allies but enemies. Time to go hunting. Kill all the enemies you come across, take their forts and … you know. Rule your lands. I sent Ivan out with the main army while using Anastasya to keep the home areas secure. With Ivan, I went straight for the jugular: attacking the town of Caer Griobta (it lies to the north of your starting position). Once you have taken it, start building it for more creature growth. Just next to the town is a green seal (which you can open). Go through it and don't listen to Amilcar, keep going. Head across the bridge and flag the dwelling, then take the boat to the small island, where you will find another sword piece. Further north still is a building with a cool illusion around it. Move up to it and Ivan will say that he now understands Tanis' story. Pick up the last sword piece and attack the prison tower. This time, your Dungeon opponents have more of an army to resist you with:
They're fortified, but vulnerable to low morale, so take out their ranged stacks asap. You have fliers, so use them. The dragons that joined me earlier really come in handy here: I gave it “inner fire” and it took out three stacks in one breath. Dragons rule.
When you have won, go back down the hill and talk to Murazel. Then Nolwenn joins your cause too. She's pretty pissed at her dad, guess that'll happen when you try to kill your daughter. I sent her on a trip to gain levels and visit boosters. Ivan needs only go straight into the Underground via the passage right next to Murazel, and once he's down there, the last sword piece is to the south. While Ivan was down there, I moved Anastasya into the Stag lands in the northwest and took the third town. Their forces defeated, that ends the “Stag hunt” quest.
As Ivan cleared the areas in the Underground, I proceeded to take him to the memorial site: Nice sword. Beware not to continue too far further northwest with the wrong hero, that will take you into the Bull duchy and more strong enemies that may attack you.
The quest is to send Nolwenn to see the Bulls. You know, to show she's alive 'n all that. You don't have to move through the garrison, just use the Underground. Move Nolwenn close to the town (leave a slot open in her army if you want the Seraphim to join you), and there's another cutscene.
At this point you actually get to make a choice in the campaign: who to marry. If you let your heart rule, you choose your concillor Tanis, the one you love. If you want to make the strategic and brainy choice, you choose Nolwenn, who will solidify the relationship between the two strongest duchies and consolidate your power. Whichever choice you make, it does not have any serious gameplay effects; you will still win the map. The one you choose will carry over to the next map.