
It's a sort of resource race where you collect a resource, do rituals at certain points, and have a climactic final battle.

Game 2 has its own campaign called "The Vortex" campaign. DLC lords add on 1-3 lords per faction and Race DLC add on 3-4 Lords each. And those are just the base Lords and FLC lords. So if you buy just Game 2 and Game 1, you'll have access to Bretonnia (4 lords), Empire (2 Lords), Dwarfs (3 Lords, soon 4), Vampire Counts (2 or 3 Lords, can't remember), Greenskins (3 Lords), Lizardmen (4 lords), Skaven (3 lords), Dark Elves (3 Lords), High Elves (4 lords) for a total of 29 (or 30) lords available in Mortal Empires campaign. The Mortal Empires campaign is a combined map of Game 1 and Game 2, with all the lords you have access to in Game 1 available. So this means that if you own the first game, you can download the Mortal Empires campaign, which is/isn't free depending on how you look at it. They planned on having each game lead into and connect with the next.
