The Codex of Cordotha is a home-brew campaign that expands upon the Curse of Strahd adventure. Strahd has grown powerful and while he cannot leave Ravenloft he works tirelessly to do so. Using the Vistani, he is attempting to collect the Tarokkan family into Ravenloft through promises of great power and wealth. In doing so he believes the original deck of Tarokkan cards read by a powerful witch (i.e. Baba Lysaga) can show him how to escape his prison of Ravenloft.
Each member of the Tarokkan family has a complete set of cards but the original cards are dispersed throughout Cordotha and beyond. Knowing that certain powers of good will work to stop him, he has sent his Vistani out into the world to assassinate these enemies and hide any recovered Codex Pages far away. One example of such enemies is the Ward Dwarves and their own codex which could effectively ‘block’ the Tarokkan family from using their own powers.