Tainted

Strong demons — the heroes of their kind — can corrupt individuals, tribes, or even whole species. The victims must drink of the demon’s blood. This act begins a transformation, taking anywhere from years to generations to millennia, that converts the creatures and their descendants into demons. Those who have begun but not completed this process are tainted creatures. Tainted creatures typically serve the Burning Legion in one fashion or another. Tribes, nations, and species that accept a demon's pact become tools. Individuals worthy of personal recruitment often become the lieutenants to powerful demons, experience compensating for their innate inferiority. Tainted creatures have a demonic awareness of the physical world, giving it blindsight out to sixty feet. In addition, tainted creatures who have recently consumed the blood of a very strong demon gain the ability to cause fel damage: All of a tainted creature's attacks do fel damage, including attacks made with weapons.

Tainted is a template that can be used on many creatures. Tainted orcs are the most famous example of them.