Esrolian Spirit Societies
Here are a few spirit practices I thought about and could flesh out if Jon picks one for Imarjan. With Chris' ok, any of them could be something the clan shaman is familiar with. This isn't an exhaustive list (unless Chris says it is.)
Imarja is a Great Spirit of Esrolia, far to big and grand for most mortals to access directly or to develop a personal relationship with. But she is generous and loving, so provides some helpers for those who honor her. These are the common magics of the typical good people of the land.
Many practices exist under Imarja's wing, and others exist that are not anathema to her. An Esrolian can honor Imarja while still being in a practice not of her, as long as they are not enemies. A Practice is part of a Tradition, and a Tradition may contain many Practices, also called Spirit Societies. I'm going to name these and give a tiny bit of detail about them.
Ancient Bear Way
In the Great Darkness, when the gods were gone, people turned to many wild spirits. Ancient Bear requires much propitiation, but shows how to protect the home and survive in bad times. Her fierce followers must attack and kill or drive off anyone who enters their home without invitation or permission. Followers are rare in modern times.
Six Friends Brotherhood
When the Pharaoh proved himself the the God King of Kethaela, one of the proofs was bringing the spirits of the six lands into harmony. Followers of the Six Friends are friendly with all the landscape spirits of country, and must not offend them. Friends may never be the first to strike or harm any citizen of another of the Sixths, but they are free to be hostile to members of their own Sixth. Spirits are varied, but usually bound to a place.
Coven of the Earth Witch
A child of Ga and half-sister of Ernalda, the Earth Witch's real name is only known to those close to her. Only rarely joined by men, the Earth Witch requires harsh proofs of those who are not her daughters, but all worshipers have power over the spirits of the earth, something even Ernalda does not have.
Cloud Walker Society
Attuned to the spirits of fog and cloud, members stay to the highlands as much as possible and, when pressed, sometimes claim to be able to walk out into the fog, or across clouds. Sometimes to cross a gorge, sometimes to enter the spirit world. Sometimes monsters come out of the clouds, silent and bloodthirsty. Then the Cloud Walkers are a clan's only protection.
Black Face and Cloak
Xentha, the Night, took many lovers when she covered the earth. Sworn to never start a fire after sunset, her followers are marked with a whole face black tattoo and a fetch bound in an otherworldly cloak. All spirits of this tradition are darkness spirits.
Excellent!
Each one of these is appropriate for Imarjan. I like the idea of the ancient bear way because it is rare in modern times and the tribe is xenophobic. The Six Friends Brotherhood appeals to the "Pavisite" in me. The coven of the Earth witch seems like the best option for Imarjan, if he can meet those difficult requirements. The cloud walker society sounds exciting and fun, but Kirk's character has cloud magic. The coolest, in my opinion, is Black Face and Cloak. Imarjan would choose it if he cannot make the grade and become a rare man in the Coven of the Earth witch.
Imarjan has spent his short lifetime interacting with the benign spirits of nature, feeling more comfortable on a hillside full of earth, water and wind spirits than at his family's dinner table. To earn a place in the coven is Imarjan's choice for his shamanic path. This aligns with both his Spirit and Earth runes.
Earth Witch
Earth Witch is something from Canon, not made up by me, though the color on it was.
Chris, I can describe it further if you need it, but it's basically the culturally accepted method of interacting with Earth spirits, as opposed to the priestess' Earth Daimones.
Myths
David Dunham suggests:
As for myths involving Xiola Umbar and Orlanth:
Xiola Umbar might be worshipped by some of the Orlanthi who live close to troll lands:
Soothing Touch is a gentle spirit of healing. She can only be contacted at night, and her powers are best against fevers. She's also known for the ritual which transfers childbirth pains to the baby's father. Many outsiders identify her as the troll goddess Xiola Umbar for this reason, though the Mokevogi vigorously deny this. Her statue of crudely carved stone lies in a sacred grove. Healing spells cast here are more powerful than usual.
Cult of Xiola Umbar = http://www.glorantha.com/library/religions/cult-xiolaumbar.html