An influential kingdom during the era of The Resundering, whose capital was situated among rolling grasslands where the low desert of Portund once was located. Home kingdom of the titular Glaivemistress of Book 13. When she refers to it as a place untouched by war, famine, or strife, Ronard the Medium comments that this must be true because the delicate gleaming crystal armor of the Glaivemistress could have only been crafted by a kingdom with only a secondhand knowledge of war craft.
Founded in 25,610 by King Yunightus, the kingdom of Arvalyyon, held sway over all the lands of Battal for the next 503 years. This era is referred to as the Peace of Yunightus (sometimes also called Pax Yunightus), marked by a marked unity of language, culture, and religion. In 26,113, the kingdom of Arvalyyon is overthrown by several lurking evils which were not expunged from the outlands of Battal. While knowledge and the arts had flourished during this period, little was remembered of the tactics of war or defense.
The relatively short war that ended the Peace of Yunightus came to be known as the War That Ended the Peace.