From The Heretic Knowledge Vault
The Millenarians are important in the Errant Road "story," because Father Egbert of the Veracian mission in Kiyoka, whose mysterious flight from the mission has launched a major thread in the game, is a Millenarian. The party that sets out looking for him (Argus, Brother Miguel, and Sister Rose, eventually joined by Lillith and Sasha) checks in at a Millenarian mission in Saus that's the repository for genealogical records that they hope will help them find Egbert. Unfortunately, this mission is heavily damaged by a suspicious fire and they don't learn much, other than that Egbert's sister Mildred Hamael, nee Kankaniel, was originally from somewhere in the Lorenzel area -- which means that Egbert probably was too.
We don't know much of the doctrinal nuances that separate the Millenarians from the regular, "Orthodox" body of the Veracian Church. Apparently they aren't large; Miguel has opined that they're the most nearly orthodox of the minor denominations of the Church. One important difference is that they don't believe in the specific existence of Hell, which turns out to be significant as the crew tries to understand just what caused Egbert to do a flit. Another difference (at least we think it's a difference) is that, judging from the Bindiel family, they practice polygamy.
Miguel has implied that the Millenarians are somewhat more common in the southern part of Veracia than in other rural areas of the country. However, the only south Veracian towns where they have been seen to have a temple are the weird Provatiel, where "temple" doesn't exactly do the thing justice, and Ramanzel, which is just ... weird. Indications are that the Millenarians aren't viewed with much affection in some of the other towns there. There's also a rather decrepit Millenarian temple in Salticiel, another of the southern towns, but it isn't clear yet whether it's used for worship, or for ... other things.