Richard IV was the son of Richard III Karthmere, known for being heralded as Thyllanor's greatest highlord -- his father's reign came on the heels of his great-uncle's, Nobilis Karthmere, who is conversely held as not just the worst highlord of Thyllanor, but is frequently mentioned as one of the worst leaders of any government in history. Unfortunately, for this distinction, Richard's reign is often overshadowed; he did not do much to combat this reputation, either, which had already existed when he took the throne in 218 AC. It was commonly accepted that Richard IV, while a competent ruler within his own holdings nonetheless, would not be his father's equal even before he died.
The primary goal of Richard's administration was to maintain the policies and his success that his father had established; he was educated as a diplomat in hopes that he would continue the cordial relations that his father had established with many of Andoras's nobles. He was successful in this regard; Thyllanor continued, more or less, along the trajectory that it had been on since the end of Richard III's reign. Where Richard IV differed compared to his father, however, was that he took the example of his father's laid-back attitude for granted, and falsely assumed that the act of ruling would come as naturally to him.
Not being gifted in the same way that his father was in regards to putting off important tasks and completing them with a great degree of success just before they had to be completed meant that Richard had to either adapt to a new form of leadership that he had not been confronted with, or rely on the strong council that his father had left behind; Richard opted for the latter most of the time, leading to his reputation for being lax and too agreeable for a highlord. The principalities of Voyatia and Colburgh grew in power and influence in response to this, and whispers of a democratic revolution permeated the court even then; it would take another hundred years after Richard IV's reign for the principalities to join the Farrowhalt Freehold and be granted independence by Richard's great-great grandson Dalan I Karthmere during the Farmers' Revolution, in response to the growing animosity towards House Dragomárus and the Kingdom of Andoras, and in particular, its ruler Aeganar IV. Richard personally was favorable towards the Dragomari and was known to have been friends with a number of lords from the family, which by Richard's own estimation was due to his frequent trips to Dragonspire City with his father when he was the King's Hand.
Richard IV died on February 27th, 231 AC at the age of 53; he had suffered from a particularly vile case of consumption that began plaguing him at the start of the year, and his death was expected for several weeks. His son Malveus II Karthmere took the oath of sovereignty beside Richard's deathbed and was coronated within two days; he dedicated his first official speech to the efforts of his grandfather and father, and later used their examples and their powerful council members as inspiration to develop the groundwork for the bureaucratic Thyllanorian government, that would itself be codified in law when Malveus died and his son Vicede II Karthmere took the throne 41 years after Richard's death.
The current Highlord of Thyllanor, Dalan II Karthmere, is said to resemble Richard IV highly.