The dungeon regulation the AI altered to let outsiders enter Faction Wars as hired soldiers.
Baroness Victory explains that the bulk of the enemy's forces are Mercenaries because the AI changed the 15K rule to allow outsiders into the game. The consequence is that most of the people the Princess Posse will face were not born in the dungeon and have no personal stake in it.
Victory treats this as an exploitable weakness rather than simply a numbers problem: outsiders will not want to wade into a real battle with real consequences, their warlords are warlords in name only, and their officers mostly lack real combat experience. The rule change is thus the single reason 100,000 troops are massed on the border, and also the reason those troops may break.
The altered rule that flooded the ninth floor with outsider mercenaries.