Kingdoms are meant to add an important strategic resource to the game. Players are responsible for the defense of their cities, forcing a balance between gaining new ground and protecting what's already there. Players will also be granted a variety of different heroes, mounts, and pets, all of which have special development paths to give player forces a unique flair. There's no word yet on when the game will go into general release, but potential players can register for the upcoming closed beta on the official site.
[Source: Aeria Games press release]