It was formed over the decades following the Divergence, when small civilizations (mostly humans and halflings) trying to survive in the Marrow Valley began to prosper after the founding of Zadash, a city that would become a haven for the people and a center of agricultural expansion. This city was ruled by the Julous family, who claimed to come from a noble lineage dating back to before the Calamity; their leadership allowed the Julous Dominion to be instituted, though not everyone in Western Wynandir wanted to join, and some would found their own independent city, Kamordah, accordingly.
The Julous Dominion was the last state to be conquered by Dwendalian Empire during the Marrow War around 545 PD, after a period of tense peace in which both nations traded but secretly tried to find out each other's weaknesses. The Dominion's capital city was Zadash, which was also the last Dominion stronghold to fall during the war, and where Manfried Dwendal executed Baron Inock Julous and Baroness Tessandra Julous, claiming that they had tried to kill him during the peace negotiations. As opposed to erasing Dominion society, the Dwendalian Empire merged their own way of life, laws, and rules with those of the people of Zadash and adjusted as they saw fit.
According to Simone Deepwell, a major battle in the Marrow War was fought in or near Felderwin.
Mollymauk Tealeaf found an old, rusted helmet in a graveyard near the Amber Road between Alfield and Zadash, which was recognized by Caleb Widogast to be a relic from the time of the Julous Dominion.
