- "Mark my words, the Imperial banner will be flying above Summerholm by midsummer."
- ―Dread Empress Regalia II, shortly before initiating the Sixty Years War
The Sixty Years War was a conflict that took place around a century and a half after Dread Empress Triumphant's Conquest of Calernia. It was fought between the Dread Empire of Praes and the Kingdom of Callow, with the Principate of Procer playing a small part as well. It took the titular sixty years and is considered one of the most brutal engagements between two sovereign surface nations on Calernia, leaving both Callow and Praes on the brink of collapse.
After the Fourth Crusade was repelled by Dread Emperor Terribilis II the young Principate has turned its eyes on Callow. Its conquest of the kingdom was successful and it occupied it for an unknown period of time, though it was likely no longer than a decade. The princes had attempted to crown one of the slain king's children to use as a puppet however Juliana Fairfax slit her throat before proclaiming her rebelling cousin - Henry Fairfax, the Landless - as her heir. He was later declared as Damned by a religious conclave held in Salia.
- "If my allies were half as reliable as my enemies, I would have a different moniker."
- ―King Henry Fairfax, the Landless, upon being told of the Praesi invasion of Principate-occupied Callow
The war started when Terriblis' successor, Dread Empress Regalia II, invaded the still occupied Kingdom of Callow. Even though Regalia the Second started the invasion she never saw the end of it. It's likely Henry Fairfax died during the war as well though this was probably much later as Callow was largely successful in repelling the Praesi invasions. According to Black, a "parade of Emperors and Empresses" had waged war on Callow during those years, ending with Dread Emperor Nihilis.
Despite both nations being ruined by the war, the Duchy of Daoine had remained largely untouched as it didn't engage in it fully. The exact details of the war are unknown but it ended because neither polity could afford to wage it anymore. In fact, no official treaties were signed at the end.
During the course of the war, several Dread Emperors and Empresses were known to rule: first Dread Empress Regalia II, followed by Dread Empress Maledicta II, whose assassination was followed by a twenty-year interregnum without a Dread Emperor known as "Haider's Reign" or "the Throneless Years". This period was brought to an end by Dread Emperor Victictive I, who was eventually overthrown by Dread Emperor Nihilis, who ended the war.
The war had a profound impact on both Callow and Praes. The memory of Henry being declared a heretic is still a sour note among Callowans and is one of the reasons for their animosity towards Procer. It's also probably had a significant effect on their economy and populace.
For Praes, the end of the war brought forward a century of mediocrity. The cultural change was highlighted by a song known as the Tyranny of the Sun. Black speculated the continuous failures with no gains dramatically altered the nations cultural landscape.