The Harvest Ritual is a ceremony that is performed by those in the New Orleans witch community who practice Ancestral Magic. This sacrificial ritual is performed once every 300 years as a means to strengthen the connection between the living witches of New Orleans and their deceased Ancestors, from whom they draw their magical power.
The Harvest ritual involves appeasing the witches' ancestors by giving them an offering of power in exchange for the Ancestors strengthening the coven's connection to their magic, which weakens over time. The offering is meant to prove the coven's faith, not only in the Harvest ritual, but in the Ancestors themselves and the ancestral magic that the New Orleans witches, both living and dead, practice. To prove this faith, the coven sacrifices four young witch girls who are put in a kind of limbo for the duration of the Harvest ritual. Then, the coven is rewarded by their Ancestors for their faith and their offering of power by resurrecting the four girls and making the coven's connection to their Ancestors' magic even more powerful for the following three centuries, until the ritual is to be performed again, a stage that is known as the Reaping.
The Elder who performed the first attempt at the Harvest ritual, Bastianna Natale, explained that the Harvest works much like the adage, "You reap what you sow." This means that their coven is rewarded for "sowing their seeds" (or, in their case, sacrificing their four young witches) by allowing them to "reap" the additional magical power given to them by the Ancestors in return for their sacrifice.