Renaria

Renaria was a kingdom that at one time held the whole of Horizon under its influence. It came into being after the warlord Tron Renaren led a successful campaign against The Aeturnum Elves and seized Horizon from them.
It was under Renaren and his line's rule that Horizon began to take on its modern form. Cities such as Fendelen, Azure, and River Run were founded as gifts to the generals and advisors who helped win the war for Renaren. Renaria also saw the re-settling of Precipice and the creation of the Ardland Highway that facilitated the stone city of Nordstar.
Renaria prospered for nearly 250 years until Renaren's dynasty was abruptly ousted from Crucible with the assassination of King Merthyron III at the hands of The House of Phantoms. With the line of succession so thoroughly fractured, what followed was decades of brutal warring between Horizon's noble houses as they vied to fill the vacuum. Eventually, it was the House of Phantoms who put a stop to what their actions began.
During the lengthy civil war, each of the factions made plays to earn the loyalty of the Phantoms, but they were, all of them, deceived, for the Phantoms had their own machinations. They made tentative gestures of acceptance to each faction's offer and in the end betrayed them all, planting a puppet on the throne. Through proxy, the Phantoms ruled for over a decade before they were overthrown during a rebellion led by a coalition of minor noble houses from Renaren's day.
These minor nobles installed a new king of their own, but by then, the damage to the realm had been done. Renaria had been all but dissolved during the civil war and the remaining cities became all but independent kingdoms. The deterioration of a standing army also allowed the wilds to encroach on trade routes and further force the now city-states of Horizon into isolation.
Despite this, the ties between the likes of Fendelen, Azure, River Run, and Crucible were never formally dissolved, nor did the former ever crown a true monarch, electing instead to maintain the structure of baronies or earldoms. Indeed, when Dorian Havik came into power in 1217 EP, he used these channels to help establish the United Northern Realms, something that very much resembles the lost kingdom of his bygone ancestor.