Initially, I was disappointed to hear that, after the Forsworn's portrayal in Skyrim, the Reach natives would once again be antagonists in the Elder Scrolls Online. I had been hoping that perhaps at least a few of the clans would side (begrudgingly) with the Daggerfall Covenant or Ebonheart Pact, perhaps on the condition that their sovereignty would be recognised, but it would seem that their insular nature and their violent history with the confederations surrounding their lands has driven them into an alliance with Molag Bal.
As one might deduce from my Briarheart avatar, I'm quite the Reachman enthusiast, so news of their being enemies to players once again saddened me. Not only because it meant it would be harder for me to shoe-horn the notion of a Daggerfall Covenant Breton avatar being a Reachman but also because I assumed this meant that, being presumably unable to engage in dialogue with 2nd Era Reachmen, we would have little opportunity to learn more about them.
However, I have found 3 in-game books (at this time) that give interesting insights and fuel for speculation regarding the mysterious natives of the Reach:
http://elderscrolls.wikia.com/wiki/Clans_of_the_Reach:_A_Guide, http://elderscrolls.wikia.com/wiki/The_Glenmoril_Wyrd and http://elderscrolls.wikia.com/wiki/Witch_Cults_of_Northern_High_Rock
Clans of the Reach gives us a glimpse into the customs of 3 different tribes; the Boneshapers, the Rageclaw and the Stonetalon.
The Boneshapers are described as having many rituals involving "thorny vines and plants". Odds are that this refers to the Briar Hearts which we encountered in Skyrim. Plants with the power to create powerful, unnaturally living warriors who share the flower's name. Interestingly, the book states that this "plant does not appear to be native to the Reach" but the clan cultivates it well. This may explain why, even though we come across many Briar Hearts lodged in the chests of angry Forsworn, we do not find them on any of the Reach's harvestable flora.
The thing I find to be most interesting and surprising about the description of the Boneshapers is that some of the rituals involving these plants "make use of the dead" but "necromancy appears to be forbidden in the clan". Would this mean that Reachmen of the Boneshaper clan view the creation of Briarheart warriors as different from the art of necromancy or is this perhaps a taboo that was abandoned in later years, particularly as the more extreme Reachmen in the Fourth Era are fighting the Nords with desperate tactics?
(Maybe necromancy, as a 'clinical' school of magic, using remains of the dead to serve a living master, is forbidden, but the nature of the Briarheart ritual, wherein a Reach warrior offers himself up to become undead willingly and remain somewhat sentient is acceptable (or even encouraged!)? This might account for why Red Eagle seemed ready to accept the hagraven's offer to (presumably) become a Briarheart.)
The Rageclaws are listed as having "domesticated a breed of stout, battle-ready ursines". They have a http://i.imgur.com/FfBvgWV.jpg...! They are matriarchal and expansionist, absorbing smaller clans. Women who are new to the clan often enjoy new freedoms whereas men that are new to the clan must earn their place by winning a fist-fight against one of the clan's bears!
The Stonetalon seem to be a mysterious lot. Less aggressive than some of the other clans and, like the Rageclaws, are matriarchal. However, the few clan-women that outsiders might encounter are "covered in heavy cloaks made of bird feathers" and seem to be "struggling through a series of trials". To me, this seems to allude to a practice whereby the Stonetalon clan encourage many, if not all, of their female members to develop into hagravens. Whether this is to bolster their combat abilities or is indicative of some religious adherence (likely to Hircine) is unsure.
It seems as though each of the clans described possesses part of the culture we have seen practised by the Forsworn in the Fourth Era. I'm curious as to whether this is indicative of the clans becoming more homogeneous over time or that living under Nordic rule perhaps forced the clans to become more unified. Solidarity in the face of adversity and all that jazz.
The book 'The Glenmoril Wyrd' reveals that the Reach Clans of the 2nd Era were not necessarily hostile to all outsiders, stating that several of the clans had good relationships with the various Glenmoril covens. Specifically, the Hagfeather Coven, worshippers of Namira, the Markarth Sister, who revere Mehrunes Dagon, and others such as Rimerock Wyrd.
They are, however, at odds with the Ilessan and Viridian Wyrds likely because of differing approaches to the veneration of Hircine. These Wyrds preferring to focus on the "less-feral aspects of Hircine" and the Reach Clans relishing in Hircine's vicious side, "celebrating lycanthropy as a gift".
This to me shows that Hircine is a canon member of the Reachmen's pantheon of 'Old Gods' and strongly suggests that Namira and Mehrunes Dagon are also members of that pantheon. Namira seems highly plausible because of Reach-Magic's love-affair with death and decay (Briarhearts and Bothela's alchemical dialogue). Mehrunes Dagon seems like a sensible addition as well, considering that his sphere encompasses revolution and change. Two qualities that are presumably very important to the Reachmen.
As it stands, my speculation on the membership of the pantheon of 'Old Gods' is; Arkay, Dibella (both have shrines in Forsworn settlements), Hircine, Namira, Mehrunes Dagon, Malacath (cos of history with orcs), Mephala (because of Reach-Magics focus on potions) and Lorkhan (chest cavities).
Another thing that I thought was worth noting was The Glenmoril Wyrd and Witch Cults of Northern High Rock's description of the witches of these covens actually revering nature, rather than seeking to defile or warp it, as some seem to have deduced from the nature of our interaction with witches in Skyrim. Considering the friendly relations between the Reach Clans and several of the covens, this, to me, suggests that religious practice among the Reachmen also puts a focus on celebrating nature, rather than defiling it. This leads me to believe that the bloody display on the shrine to Dibella in Broken Tower Redoubt is actually evidence of sacrificial worship, rather than anti-Aedric desecration.
Many thanks if you read through all that rambling. I thought some of the lore forum visitors might appreciate having these books identified as I know that at least a few people are Reach Native-enthusiasts like I am.
I would like for this thread to encourage discussion, but I understand I haven't presented many questions. Please, feel free to address some of my speculation.