Bronjahm was the foreman of the soul grinder engines. After learning from Kel'Thuzad himself the value of souls and how to grind them down to fuel the engines of the Scourge, he patrolled the Forge to ensure that no interruptions befell the engines' operation.
In the introduction cutscene to the battle with the Jailer, it is revealed that the soul grinders were built to extract the world-soul of Azeroth, channel it through the Spire of Icecrown Citadel and the Pinnacle of Domination of Torghast, and deliver it into the Heart of Eternity.
- Sleeping flesh giants can be seen in the background of the Forge of Souls, implying the souls are used up to power them.
- Although they are the primary set piece for the dungeon, especially Bronjahm's fight, they are not directly interacted with or mentioned in dialogue.