Master Otigha had been planning for this escape for quite a few days.
After the Battle for the territory, all the prisoners of war were kept confined in the large cave on the second level of the Red Earth Highland. Slaves and members of the vassal clans took turns in guarding them in three shifts; there was no door to the cave entrance, but a rough line was drawn with chalk. Any prisoner who crossed this line would have to bear the severe consequences— as the ones who tried found out when their bodies were torn to pieces.
Master Otigha and his apprentice, due to their unique statuses, were kept in a separate cave under the watch of four Bear Goblin slaves who simply stuffed food into their mouths at meal times.
Confining a mage is not the same as restraining an ordinary person. The enemy had made a small mistake due to the lack of individuals skilled in this task.