Pocket Universes (1981 Wereskalot, orange B3, AC2, B8)
by Sionainn T. Mac InnéirgheIf a module has a Official placement on Mystara, but highly conflicts with the mainline continuity, I suggest designating it to be a Pocket Universe (in BECMI terms, a.k.a. a Bounded Plane), an Island Plane (in WotI terms), a Half-World (in 2E Die, Vecna, Die terms), a Demiplane (in 3E terms), and a Domain of Dread or a Fey Realm (in 4E and 5E terms)
Castle Amber already provides a BECMI precedent for effectively delimiting a Pocket Universe with impassable gray mist. Though the Mists of Ravenloft are well described, and would be applicable as the border of the Surrounding Lands (of B3) and the Swamp of the Hideous One (of AC2), the gray mists of Castle Amber could be used for the non-dreadful boundaries of the The Rock and Sylvanhome, as a Fey Realm. The "void" described as the edge of Half-Worlds in 2E is also relevant.
The Surrounding Lands near the Palace of the Silver Princess
"This is a ruthless place filled with terror. The ruler of this chaotic nightmare is Lady D’hmis. She rules this barony with a firm and unforgiving hand."
I would make the Palace of the Silver Princess (orange-cover version) into into a Domain of Dread ruled by Lady D'hmis. Along with the Barony of Gulluvia, the Shire of Deadmule, the Canton of Velders, the Dwarf Kingdom of Anteria, and other lands which were only mentioned in Orange B3. The barely mentioned places (e.g. Lordship of Westford) would be be located on the eastern marches, or to the west and north on the Adri-Varma Plateau. The Plateau as a whole would serve as the shape of Domain in Ravenloft.
The Officially bare desert cactus-filled version of the Plateau would be what replaced the terrain after the domain was ripped from Mystara.
Swamp of the Hideous One
The Darklord Rosentos, the Hideous One
Also includes the ruined (1981) lycanthrope-infested version of Wereskalot; otherwise, there would be nothing notable located along the western river branch of the AC2 map.
Question I have for myself: was the place already a Domain of Dread before Rosentos' and his soldiers ventured there? Or did it only move to Ravenloft after he became a vampire? Some of the features the soldiers encountered, such as the hindering "spirits" referred to by Grisbaldos, and their very unlucky travel logistics (7 days to march from Luln to the Cruth River), suggest that the place already was in acursed Ravenloft. When then would beg the question: who was the Darklord before Rosentos?
The Hall of Rock: A Fey Realm
Fey Lord: Master Lirdrium Arkayz
Even though I myself went to great lengths in mapping out the Official location of B8 "on the river northwest of Threshold", I acknowledge that the other good option is to make is to consider B8 to be a Pocket Universe (in BECMI terms), and a Fey Realm (in 4E and 5E terms). It would be surrounded by mountains. Perhaps it moves around to various locations, such as the five Official placements listed in B8.
There are already fey elements. Sylvanhome, the Greenweald, the elves, sprites, gnomes, and goblins. Lirdrium Arkayz could be, in 5E terms, statted as a Fey-pact warlock. Is there an Arabian-themed fey lord in D&D?
A different but related case is...
The Isle of Dread: A Teleporting Island from the Plane of Water!
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These Pocket Universes could even be marked on a map of the Known World. Though they don't exist in the Prime Plane, travel to and from them could be easier at certain "equivalent" places on the map.
The Ruins of Wereskalot
I’d also add that the Ruins of Wereskalot (the ruins depicted on the 1981 Expert map) could be its own lycanthrope-theme Domain of Dread, separate from the vampire-themed Isle of Rosentos.
Either as a single 6-mile hex, or including the left branch of “the great river” from AC2, since there is literally nothing (no encounters, nada) located on that branch.
And in my placement (7 hexes west from Luln), the wellspring of that branch is just at the south edge of Wereskalot. This branch could be named “Wereskalot River.” The boundaries between the two Domains would be at the fork, where it meets the Great River.
The Five Shires GAZ is ambivalent as to whether there are lycanthropes there. But in that depiction (as per the change in the 1983 map), it’s a Village, not Ruins. I suggest that the Ruins, and (most of) the lycanthropes, dwell in a Pocket Universe (in BECMI terms); and a Domain of Ravenloft, on the Shadowfell (in terms of later editions).