Warlords is the first expansion of Civilization IV. It includes: A new unit for all civilizations, the warlord (a military leader) who provides new abilities to units.
A unique building for each civilization, as they have a special unit in the original game.
6 new civilizations
10 new leaders
A new diplomatic option, the vassal state
2 new traits for leaders
3 new wonders, including the Chinese Great Wall you can view from space.
6 historical game scenarios