Dragon's disciples were the strongest reoccurring character in the novel, and they foiled the plans of the followers of Chaos many times.
In the second volume, they were confronting the main forces of Chaos and the undead army, stopping them from invading the northern dukedom and the nearby counties and pushing them back, creating a safe zone for humans in the north, while the protagonist was struggling to survive against the servants of Chaos and reach the safe haven the dragon disciple's had created.
During the invasion of Chaos, which sadly didn't reach a conclusion before Roy encountered a dungeon break and got killed by a beast back on Earth, Chaos would have enslaved all of humanity in a year if not for the Dragon's Disciples interference.