Warring Valley Period < 0
The Warring Valley period, referring to the pre-history of Barovian Calender Events, occurred in the Age of Giants and was not well-understood. Great battles were fought between Dragons, Giants, and various Mortalkind at the beginning of this time, but eventually, the ancient creatures of the world were driven east to the Body of the Greatwyrm. The center of this history was in a valley in the Balinok Mountains; however, even this place was not highly desirable or conducive to the life of most smallfolk. Over time, Dwarf clans would move west to Skypeak as the few remaining Elf tribes disappeared into the forests. This left mostly-Human mountain tribes to fight over land, disparate groups who would define their own cultural practices and forms of worship.
The later Warring Valley Period was characterized by the establishment of noble houses and true human settlements in the valley, and the induction of the Barovian Calender Timeline. Trade from areas south of the Crowncrests brought changes to the valley, including languages, customs, and religions. These ideas causing tension between old worshippers of the Ladies Three and followers, of Thestus, the "morning lord".
By the end of this era, most of the trade and wealth came through the "gateway to the valley", the Village of Barovia. From their seat as rulers of the settlement, the von Zarovich family gained undue influence over the entirety of the region, eventually naming it the Zarovich Valley, though never had complete dominion over their namesake.
Common Era 230 — 351
The von Zarovich family, once dominant across the valley, only controlled the eastern Village of Barovia ever since the ratification of Common Unification. As rulers of the "gateway to the valley", they believed they deserved further dominion, and over hundreds of years, their influence grew. Petty squabbles and political intrigue occurred at the beginning of this period, but most houses were more concerned with protecting themselves from raiding tribal-folk who worshipped the Ladies Three.
Violence ramped up near the end of the era, as the warlord Strahd von Zarovich reconquered the valley in his family's name. This period was filled with many minor battles, assassinations, and coups, all enacted in response to von Zarovich rule. Eventually, Strahd succeeded in quelling nearly all of the valley's disparate powers, and placed control of the region back under one rule, all devoted to serve Castle Ravenloft.
Rule Of Strahd 351 — 735
The Rule of Strahd era marked the rise from the Counthood to near-godhood of Strahd von Zarovich, as his pact with Vampyr and slaying of the Ladies Three resulted in him having full dominion over the land. Mists encroached on all sides, and Barovia was removed from the Material Realm into a demi-plane of the Umbral Realms. The souls of its residents were trapped in this era, cyclically repeating throughout generations. Much of this period remains unrecorded, as both records and record-keepers were destroyed by order of those bearing the Mark of Strahd.
Era of Dawn > 735
After the Heralds of Dawn completed the Slaying Of Strahd, Barovia was completely altered. No longer under the influence of the Darklord or a Dark Power, the landscape returned to as it had in the time before Strahd. The valley remained trapped in the Umbral Realms, and at risk of planar threat, as its denizens rebuilt the valley that their ancestors once knew.