By 1255 the Pitch Bone Legion had grown to more than 2,000 undead. This horde was under the control of the Cult of Worms. Under the direction of this evil organization, the undead ravaged the lands of Kal-Oni and battled the armies of Kal-Oni. They destabilized Kal-Oni territory and caused such turmoil that an opening was created for those unhappy with current government. In 1260, the Kal-Oni War started. During this conflict, the Pitch Bone Legion continued to threaten both sides of the new conflict.
In 1266, a civil war and ruinous attacks by the Pitch Bone Legion cumulated in fall of Kal-Oni. The Lances of Merioss, alliance member of the Gwaeldior Alliance, marched against the undead so that they would not continue to threaten the people of Hells Womb. The battle was fought in the Mynzuth hills and plains east of Bathor. The Lances of Merioss destroyed the entire undead horde of the Pitch Bone Legion.