From "Adventure Summary and Background:"
Since Leonydas val’Virdan, the Sword of the Heavens conquered Nishanpur; many citizens are divided in their loyalty. This is especially true among the noble houses in Nishanpur. Although the Sarishans seem complacent to the rule of the Cleansing Flame, there is a Sarishan faction called the Brotherhood scheming to overthrow the Nierite rule.
In the past year, there have been some ill omens for Sarish, such as the mysterious death of many cats (So Shall Ye Reap). The Brotherhood decided to take advantage of those omens and started to spread rumors of Sarish's power weakening, and that infernals are coming through the Wall of the Gods.
The Brotherhood have been ambushing the Swords of Nier with summoned infernals near the Wall of the Gods. To further their plans, they are secretly creating defective Sarishan steel weapons for the Swords of Nier. They hope to escalate the affair into a crisis, and lure the Swords of Nier away from Nishanpur.