This article talks about the Chosen as a concept, for the game Blood II: The Chosen follow the preceding link.
"Caleb, Ophelia, Ishmael, Gabriella - these are the Chosen. Former generals of a defeated god, they must now fight the Cabal together in an uneasy truce. What are their true ambitions?"
--Blood II: The Chosen website
The Chosen were the elite generals of the Cabal, named for their specific selection by Tchernobog. The Blood II website implies that there have been others in the cult's history, but not very many. After the sixteenth incarnation of Tchernobog's betrayal of his Chosen, they ultimately became the Cabal's greatest enemy following the resurrection of their leader Caleb. The Cabal did attempt to train a new group of Chosen after the fall of the 16th, but were again thwarted by Caleb. Caleb remained the only remaining member of the Chosen for one hundred years after the events of Blood.
After all that time, the other three Chosen were accidentally revived due to reality fluctuations involving the Singularity Generator under construction by CabalCo industries. They then proceeded to assist Caleb in defeating Gideon and CabalCo, as well as the invading forces of the Ancient One that followed them through the dimensional portals; during which Caleb encounters skeletal forms of all his comrades, whose veracity and connection to them remains speculative. After Caleb rebinds the realities, he and the other Chosen were then trapped in the reality of the Ancient One and encountered and fought the Nightmare.
It is unknown what happened to the Chosen after this, but the Blood II promotional material, as well as the cancelled Blood II: Revelations expansion, hint at a desire by Caleb and the other Chosen to take control of the remnant Cabal and rule the world.