A(n) is a detailed study of the life and activities of a group of people in which researchers may live with that group over a period of years.

An ethnography

Explanation: An ethnography studies the daily life and culture of a society and may involve the researches to immerse themselves in the culture by living with the group of people.  

In practice, ethnographers live with their subjects for a period of one year or more to achieve immersion while aiming to retain some detachment necessary to observe their what is unique about, and peculiar to the culture.  

it depends on which society you are referring to. many civilization performed rituals so the gods would with their growing season but the most well known is that of the aztecs. they would make sacrifices, usually animals, but sometimes humans as well.