During his governorship, there had been a rise of Chaos activity throughout the Cadian Gate and to better fight against it, a muster of Imperial forces had been ordered on Cadia's Kasr Tyrok. Porelska gave the orders to how the Imperial forces would be deployed on the Kasr, but General Creed vehemently disagreed with the Governor's decisions. Creed had long suspected that another Black Crusade was underway and that Cadia was ill-prepared to combat a sudden attack from it. The General was repeatedly ignored by Cadia's High Command though and lost any support he could have gathered, when he claimed the Governor's deployment plans were pathetically incompetent. While it was true that Porelska had last taken field command on Hydator Prime in 938.M41, the Governor's orders appeared sound to everyone but Creed.
The General however, would be proven correct when the Battle of Tyrok Fields broke out soon afterwards. With the Imperial forces packed so closely together, the Volscani Cataphracts' traitorous attack caused mayhem and allowed them to disable Porelska's Leviathan, Excubitoi Castellum. This caused its comms to go down and prevented Porelska from taking command of the Imperial forces, leaving them to fend for themselves. Soon other Chaos forces appeared and invaded the stricken Excubitoi Castellum. Left stranded and unable to communicate for help, the Leviathan's defenders were killed and, despite their best efforts to protect the Governor, Porelska was beheaded by a Chaos Space Marine. Creed though was able to rally the Imperial forces to victory and, after it was discovered Governor Secundus Karwyn had also been killed, the General became Lord Castellan of Cadia.