Having done some PF-quoting, here are some points about how I play Minmatar ritual and transcendence stuff. Usual warning about it being a big cluster, and the tribes and clans not necessarily doing things alike.
I think it's about social hacks and body hacks.
I think some of it is intentional--I can see Sebiestor, in particular, applying scientific method to their tinkering with ways to get the right experience--and a lot of it is people winging it based on things that have worked before.
I think there are huge differences in how much practitioners think is "real" and how much they think it's symbolic (although the
experience is real). Those differences parallel... let's say "the theology preached in neighbourhood churches vs the theology taught in seminaries back when seminaries were allowed free thought".
To generalise, shamans IRL are typically
schizotypal. They're the "half-crazy" people somewhere on the continuum to schizophrenia: they can function in the specific social niche of spirit-guide and mediator for the world of myth and story/sea of dreams/unconscious. I imagine EVE shamans are like this, too, with most of them having "being a shaman" as a necessary lifestyle determined by their personal wiring and demons and focused by clan recognition and training, rather than it being a chosen day job for any likely child.
That said, I do think there are probably shamans or people in shaman-like roles out there who fit more into the day-job model, some of them even being a lot like a blend of the contemporary psychiatrist/clinical psychologist/counsellor. There will be some tension about what constitutes a "proper" shaman. "Proper" half-crazy shamans will be brought in for important rituals, while you might see a tamer one for clan pastoral care. Maybe.
There will also be con-artists passing as shamans.
I think EVE shamans use and distribute pharmacological assistance as required to help achieve the appropriate state. I'm not sure that there's always a big distinction between shamans and local drug suppliers.
I think that for some clans there's a big focus on experiencing your altered states in the appropriate social setting, at the appropriate time. You might reach for those states using fasting, pain, drug-use, dancing into a trance, sex, etc. Despite the emphasis on doing things in a ritual context at the right place and time, some of these are way open to abuse, by insiders as well as by outlander "tourists".
I think there's a lot of use of metaphor and anthropomorphism in Matari religion. People keep the gods they need, and some of the gods they want. Groups and individuals might adopt new gods depending on experience: I definitely imagine people coming back from deployment with feelings one way or the other about their regimental gods. But gods can be small and specialised--like the one who requires rubber chickens to be placed in server rooms--as well as large.
In the wider sense--beyond just shamans and mysticism--I play Mata's sub-tribe's religion as being based around ancestors and erendati. Also rites of passage, roles, values and rituals.
Ancestors are, in one sense, your genetic forebears, and there are rites around death and the spirit journey, and elements of "What advice do you think Aunt Yana would give you in this situation?". In another sense, "ancestors", for Mata, refers to "the gene-wisdom": the things that humans have been selected and programmed for many millennia to do.
"Erendati" are, for Mata's sub-tribe, the spirits of things and essences, anthropomorphised as appropriate. There will be an erenda for "fire", "the void", "the river past the house", "that house", "
breaking stalemated negotiations", etc. No, I don't have a pantheon: you bring these up as you find you need them.
I think most Matari religion has been made up since the Great Rebellion. Don't tell anyone, though.
I don't judge wider Matari spirituality as good or bad. In many ways it's primarily "useful": as social bonding, for rites of passage, as solace and structure for grieving, as guidance when making the decisions of life and community. It can, like most systems, be abused and abusive. It also helps provide roles and defaults for a people who bear a lot of scars and could do with some life scripts that are reasonably effective.
For me it's tied to a sense of yielding some level of control over your self and your body to your group--being willing to blur your boundaries for belonging, and being willing to sacrifice self for the survival of your kin-group--that I, IRL, consider scary-dangerous. (Just thought I'd throw that in there since I've been idly doing a bit of a post mortem lately about my roleplay with Mata. There are some elements of the way I play Matari religion that I find congenial, and others that are definitely not.)