We need to take note that they were not forced to accept Magellan's religion, "The captain-general told them that they should not become Christians for fear or to please us, but of their own free wills... All cried out with one voice that they were not becoming Christians through fear or to please us, but of their own free will." (Pigaffeta)
Blood compact was an ancient treaty or covenant ritual signifying peace and friendship. In Spanish it is called Pacto de sangre; Sanduguan Filipino. Parties entering into a treaty would cut their wrists and pour their blood into a cup filled with liquid, such as wine, and drink the mixture.