The Jivaro's land starts where the mountain waterfalls give way to tributary streams and rivers that are unnavigable because of rapids, and ends where the rivers begin to flow more slowly and can be traveled by canoe. They live in scattered houses, each containing a polygynous nuclear family and occasionally a married daughter and step-son who have no children. Each house is situated in the middle of a large cleared out garden, on a hillock near a stream.
The garden is the province of the women of the house; the men clear the garden by felling giant trees (which in turn take down many smaller trees as all the trees are connected through their canopies by vines) but the women weed, plant and maintain the garden. The primary food crop is sweet manioc, grown for its large tubers. Manioc is not only the primary food, it is also provides the exclusive drink for adults and weaned children - the Jivaro drink manioc beer in prodigious quantities (3-4 gallons a day for adult males, 1-2 gallons a day for adult females, ~ 1/2 gallon for 9-10 year old children). The beer is typically weak, as it is usually drunk before it has fermented long enough to reach maximum alcoholic content (which takes 4-5 days).
The Jivaro also believe that the manioc plant has the innate desire and ability to suck the blood from any person touching it. To protect themselves and their families from this ability of the manioc, the women turn to a type of earth spirit called Nunui. Nunui appear as 3' tall, very fat women wearing black dresses. Nunui are responsible for pushing plants up out of the ground and plant growth in general. Nunui like to dance in clearings in the forest, and often many of them will come to dance in a newly cleared garden. However, there is usually only one nunui associated with each garden once it has been planted. The nunui stays underground during the day, and at night dances in turn with each manioc plant. Nunui demand a well-weeded garden to give them the room they need to dance with the manioc. The women also sing special songs to nunui, to give them respect and warn them when they are coming early in the morning to the garden to avoid frightening nunui away.
The female head of household will also hide three magic stones (unworked pieces of red jasper), known as the stones of nunui or the stones of manioc, in the garden - these magical stones are the babies of the nunui and ensure that the nunui will stay in the garden, the crop will remain plentiful and the women can call upon the nunui to make the manioc drink only the blood of trespassing enemies. The woman gets the stones of nunui after a nunui reveals their location to the woman in a hallucinogen-induced vision. Each vision only reveals the location of one such stone, which the woman must then immediately go out to find and place in the garden.
Anyone moving through a stand of manioc must save vs. spells each round (or make a CON save DC12 for 5th edition types) or take 1d6 damage from blood loss. The plants are otherwise normal plants and can be easily cut down or uprooted. Carrying a cut branch of manioc (or sticking it in one's belt) grants a +2 to this save.
Stones of Nunui/Stones of Manioc
Three pieces of magical red jasper. Detect Magic will reveal the form of a baby inside them. They are the babies of nunui and serve both to tie nunui to a garden and also as a conduit which allows their possessor to tap into the power of nunui to control the vampiric properties of manioc (and possibly ask other boons of nunui as well). The women that tend the garden and the husband of the house are rendered immune to the manioc's blood drain if there are stones of nunui in the garden and the women regularly sing this magical song:
Don't suck the blood of my husband
And also don't suck the blood of my daughter.
When you want to suck blood,
Suck the blood of my enemies.
When my husband comes,
he will look very beautiful and very clear.
But when our enemies come,
They will come very pale
And in the form of demons.
And you will know
Who will die,
Who will die.
And when they enter this garden,
They will have their blood sucked.
All, all I can call,
Even the plantain itself.
I am a woman of Nunui.
Note that children are not excluded; they are instructed not to play in the garden lest their blood be drained!