I'm writing/worldbuilding a dark fantasy comic set in the Bronze Age.
One of the tribes has a mother-son incest ritual where warriors, after their first human kill (usually happens between 16 and 20 years old), must re-enact a mythological scene to purify their souls. The mother of the warrior must wear a ritual costume made of vegetation and hide in the forest, taking the role of the Earth Goddess. She will hide and occassionally make animal-like calls. Her son wears pelts and skulls of various animals to take the role of the Animal God (who in mythology is the son and husband of the Earth Goddess), and he must find his mother hidden in the forest by answering the right animal calls. Once he finds his mother, he subjugates her, takes her to a ritual cave and has intercourse with her several times across a number of days, until the lack of food makes them too weak to copulate. She then leaves the cave, discards her costume and returns to the tribe pretending that nothing happened and that she was simply "lost in the woods" (everyone knows the truth, they also pretend). The son continues his existence as the Animal God for a few more days until he has to return to the village for food (he is not allowed to shed blood). He is beaten with sticks by the elders until the pelts fall off him (he is "vomited by the wolf") and he's welcomed back like nothing happened, having cleansed the stain of murder from his soul through "rebirth".
In some cases the mothers end up pregnant, and the children of the ritual become Earth Druids, who are castrated at birth and sent to live at the edge of the village at 10 years old, to mantain the boundary between humanity and wilderness through their pure spirit. They are not considered to be humans, since the community pretends that the mother was lost in the forest and wasn't involved in any way with the incest ritual: instead, she was simply asexually "seeded" by the wild gods to create a human-looking warden of the forest.