Blood Sacrifice is a national trait that allows priests to sacrifice blood slaves at temples in exchange for 1 temple check per slave. A sacrificer can use 1 blood slave per turn up to their holy level for blood sacrifice in addition to any adept sacrificer value they might have.

If there is a lab present in the province and there are bloodslaves left in the treasury the mage will automatically be assigned another slave at the start of the next turn.