From publisher blurb:
There are primeval beings that subsist on the power inherent in blood. While many of these creatures are minor spirits that stalk the edges of life, waiting for the moment when violence or a chance accident spills the liquid they crave, others are more powerful. Specters of war, torture devils, and spirits of sacrifice, all fuel their eldritch power through blood.
Warlocks forge pacts with these entities that thrive and grow on the spilling of blood. With a simple word a Warlock can call them to feed at an enemy’s wounds, increase the strength of the Warlock's magic, or even control the blood coursing through another creature. Others fear the blood-pact warlock, for just as his patrons demand his blood in exchange for power, they also thrive on the blood of any living creature -- friend and foe alike.
This pact features a full listing of powers from Levels 1 through 30, four new Feats exclusive to the pact, a paragon path, and four new magic items.