On July 31, 2007, Paradox announced an expansion to the game: Crusader Kings: Deus Vult. The game was released on 4 October 2007, and is only sold online.
The expansion pack redesigns some of the basic features of the game, such as removal of DNA inheritance of traits, religious warfare, use of friends and rivals, etc. In addition, new scripting commands were added as well as new character traits.
'Source: Crusader Kings on Wikipedia'