It's hard to differentiate between early Nefarious and the broken one, who ended up ruling Praes for over ten years. The only information available is presented from Tariq who heard rumours the Emperor had Callowan ambitions even when he was still a Claimant. Overall he ruled for a bit over ten years.
Fields of Streges
The battle that took place there was a decisive victory for the Kingdom and had severe repercussions for the Empire. Nefarious himself took to the field, battling against the Wizard of the West, while the Black Knight led the Legions against the Good King Robert and his knights.
The Wizard of the West has crushed Nefarious so thoroughly that the latter hasn’t left the Tower after he ran back to Praes for the rest of his reign. This was largely responsible for Nefarious’ incompetence as having one’s power broken is a traumatic event, especially when it’s done by external factors. The Black Knight was also killed during the battle as he overcommitted and was eventually tired out.
After the devastating defeat, Nefarious largely retreated from court. He spent most of his time studying his grimoires and indulging in carnal desires with his Seraglio. He eventually turned his Seraglio into “some sort of… sordid sex dungeon” which was taken as a sign he’d lost his ability to rule. He as far as to have his Sentinels scour the breadth of Praes for beautiful women. By and large he left ruling to his Chancellor who was the de facto ruler for ten years.
For example, the Emperor rarely attended his own Dark Council meetings, letting the Chancellor lead them instead. The High Lords and Ladies were generally unchallenged: Thalassina even tried to gain a monopoly on spice trade, nearly leading to civil war. The court of the time was describes as a “festering snake pit”.
On the rare occasions when Nefarious remembered he was supposed to rule he often had a few members of the Imperial court tossed into the arachnid pits and attendance had been, in a sense, mandatory – the Chancellor would pass along the names of any absent to the point the Emperor at them when he next felt like stabbing at shadows. It's also implied he summoned devils on the twenty-fourth floor of the Tower who later came to collect their due from the court.
There were no major wars under the Chancellor though there was significant unrest. An eight goblin rebellion nearly broke down and the orc clans also buckled under the Tower - they even stopped paying tributes.
The downfall of Nefarious was inevitable as the Chancellor had all the power: backing from the High Lords, the Legions and he controlled Ater. He was poisoned by his then-concubine Alaya of Satus who was a part of his Seraglio.
After Naferious was killed the Chancellor dismembered and burned his body, scattering the ashes so as to ensure no wraith could form. Soon after, the Chancellor declared himself to be Dread Emperor Baleful and ordered the Black Knight to hunt down Alaya. This order was refused, thus starting the Imperial Civil War between the Dread Emperor Baleful and Dread Empress Malicia.
- Under his rule Praes received a Red Letter for trying to develop a farming machine.
- Despite failing to understand Sorcerous’ room, he managed to invent a flesh simulacrum that could be inserted with a semblance of personality or soul. This was used numerous times by Dread Empress Malicia and once by Black Knight when he fought against the White Knight.
- https://practicalguidetoevil.wordpress.com/2015/06/24/chapter-13-order/ (WOG)