The Warhammer Fantasy Old World also leads to an interesting setting. There are two major good nations (the Empire and Bretonnia), three smaller nations (Kislev, Estalia and Tilea) and plenty of microstates (the Border Princes). There are powerful and isolationist Elves (Wood and High variety) and loosely connected dwarven enclaves.
Easy allies are abound in the Orc tribes and the Norscans, whilst more difficult quests might lead to an alliance with the Skaven or possibly (though rather difficult) the Vampire Counts.
Map:
The usual suspects would be:
Khorne: More or less the same as Karth, although more based around the Norscans than the orcs.
Tzeenth: Seems similar to Belial, as an all knowing God. Would be based on trickery and change (revolution etc.). I wonder if it's possible to give heroes a mutation, maybe it's possible to create a wound which won't be randomly assigned and which gives a huge malus on relations with civilized nations. I wonder what happens when a hero is exiled from everywhere.
Nurgle: Plagues, plagues everywhere. Would also have an easier time allying with the Skaven. Could probably be modeled on the Death Lord Old One once he returns in the game.
Slaanesh: The one which differs most from the Old Ones we've seen. Would have many agents focused on seduction and corruption. I think I've seen somewhere that heroes can marry, so that will certainly lead to possibilities. Also thieves guilds will be nice to corrupt, maybe focus them on brothels or something.
One problem is how to handle the fact that these are known threats and prevent random heroes from entering the Chaotic Maelstrom. Lorewise I also can't really see them waking up, so they'd have to have long wake-up times, representing the Growth of the Chaos Wastes more than anything else.
If possible to have multiple start locations there are extra options:
- The Horned Rat: Nobody believes the Skaven are real anyway, so keep it that way. Spread chaos and corruption without ever being suspected. Poison cities and fan the flames of war. Assassin Agents will roam the map and no king will be safe.
- Nagash, to quote the Warhammer Wiki: "Its believed that he is currently enacting his will in the world through the manipulation of others", he'd have control of the undead and access to extremely powerful magics. You can also use the Vampire Counts as easy allies and they are poised to strike at the heart of the Empire.