I have a couple questions and a useful thing my pagan friend made for you.
First, what's the source of evil for Naturacultists? Are there evil spirits, an evil "devil"-type figure, does evil come from the hearts of men, a mix, or something else completely?
How do you believe the world was created?
Is there a deity in charge of time? None of the elemental deities or holiday/dark/light deities seem to cover time.
Here's the thing she gave me to give you. It's how you can set up for a group of Naturacultists, also known as a solum (group).
First, you must find a tree that your solum will meet at. It can be any type of tree and any size, though the general rule is bigger and older is better. It's probably best to have it be in a place where not too many people go--you don't want to be disturbed. Once you find a satisfactory tree tie strips of cloth, ribbons, and/or pieces of rope on the branches. This sets your tree apart and invites totem animals, kind spirits, and other supernatural beings to come there. You don't have to start out with a lot, but you should add another every time you have a holiday or perform one of the bigger ceremonies. You can also tie other things up like wind chimes, bells, charms, etc.--customize it to your solum's liking.
There are a few important things you will want to have at your solum's hometree when you gather. One, you must have a bowl of water for washing hands in and to gaze at while you meditate together. Two, you must have an object which bears your solum's symbol. Every solum must have a symbol. It can be whatever you want. Third, you must have at least one naturae librum with you when you go there. There is a fourth thing you can have with you but it's not necessary if you don't want them. It's best to bring blankets to sit on while you are there--you will want to sit down. You will also need an altar, but it's up to you whether you want your solum to have one big one or have each person bring their own. It's best that the altar is either something natural, like a boulder or stump, or portable so you can pack it up when you're done for the day.
There are only a few rules you need to follow while you're at the solum's hometree. Here they are:
1. Respect each other and the deities.
2. Do not desecrate the area by leaving behind waste.
3. Companion animals are welcome, but be sure that they do not destroy the area.
4. No electronics (except phones if absolutely necessary).
5. No makeup should be worn at the hometree--you should be all natural.
6. You can wear whatever you want, but more earthy colors pertaining to the elements are encouraged.
7. You must be barefoot when you are worshipping at the hometree.
It's best that you appoint a head vates (prophet) to lead the worship. If you have enough people he/she can be allowed to have up to four lower vates.
Now I will detail a basic outline for solum meetings at the hometree:
After everything is set up the solum members stand or sit on blankets near the tree.. The head vates stands right next to the tree. He invites everyone to line up and wash their hands in the bowl and touch the solum symbol. They do and then head back and sit again.
The head vates announces any news and then walks around the hometree, reciting aloud a naturem to all of the deities while he goes around. When he finishes he comes back to the front and recites the solum's special naturem, which the rest of the members say along with him.
When this is done they do any special ceremonies that they need to do. When that is finished the head vates gives offerings to the solum's patron deity and any other deities they feel the need to acknowledge. (Each solum should have one deity that it relates to most and gives offerings to every time they meet.)
Then the solum meditates for anywhere from 15 minutes to half an hour, gazing at the bowl of water.
Then the head vatem allows people to come up and say anything important they need to say or ask for benemare.
Finally the solum sings songs, then they all wash their hands again and leave.
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A few more things:
The head vatem should probably have something special he or she wears just for meetings at the hometree, like a necklace or headdress. He or she is to be given respect, but if the rest of the solum is dissatisfied they can demote the head vatem and vote in a new one.
And yes, it's possible to have one inside, but it's much better to have one outside.
The solum is considered the guardian of the plain/riverbank/forest/whatever their tree is on/in.
(That's all she had for you.)