KonServator, it's exactly this map. I completed it on Recruit difficulty as Neutral, on Warrior difficulty as Haven, and on Veteran difficulty as Dungeon. Now I'm trying to complete it on Hero difficulty as Haven. I declined Chaos at the start. With huge armies of neutrals, it's not very effective.

I'm leveling up the Gnome with Education, Leadership with Empathy, Light with Storm, Summoning, and Luck. Defense and Combat skills are not very useful on this map. At least on Veteran difficulty, I had almost no melee battles. Everything was decided by ranged units and the hero's magic. Sometimes they were helped by Berserkers. Occasionally, bears joined the battle.

Storm is very helpful against ghosts. They don't even reach the thickest units until the 3rd turn. And Utopia is easily taken with it.