Ok,let's consider the Aztecs, safrifices and bloodletting mportant aspects of the Aztec religion, as they believed it brought balance and peace to the world around them. This was considered moral behaviour.

At the root of these Aztec rituals was the belief that the gods needed to be nourished by human blood. A part of the Aztec religion, therefore, was to participate in bloodletting, which is intentionally harming and drawing blood from the body. Those who were higher in status within the Aztec religion were expected to give the most blood during these Aztec rituals.

The Aztec gods and goddesses also required the living hearts of humans for nourishment. All hearts were good, but the bravest captives were considered to be particularly nourishing to the Aztec gods. As a result, widespread warring took place, not for territory, but for the captives back to the Aztec temples for sacrifice. Sometimes, those practicing the Aztec religion sacrificed just one person. At other times, hundreds or even thousands of captives were sacrificed at a time,


Warriors were highly regarded in the Aztec culture. They were responsible for going out and finding and capturing the majority of the sacrifices used to appease their gods. As a result, a special god was included in the Aztec religion to honor the warriors. This god, Camaxtli, was the god of war, hunting, fire, and fate. He was thought to have invented fire and to have made the Earth. The Aztecs believed that Camaxtli lead both warriors slain in battle and human sacrifices to the eastern sky. According to the Aztec religion, they then became "stars in the sky".


Source: http://www.aztec-indians.com/aztec-religion.html