The Breakers are residents of Algul Siendo, a compound located in End-World. Because of their strong telepathic skills, The Crimson King uses the Breakers to erode the Beams, hoping to cause the destruction of the Dark Tower, and the end of existence.
To feed their brains and strengthen their abilities, Breakers are fed on a special diet, the details of which most Breakers claim to be unaware of. This special food consists of childrens' brains - specifically twins, who are rounded up from the surrounding provinces and subjected to painful medical procedures. Left disfigured, deformed and mentally subnormal, the children are then sent back home with no memory of what happened.
In Other Media
Wolves of the Calla
In the fifth novel of the Dark Tower series, Roland Deschain and his ka-tet meet the families of the children who are taken away, and set out to stop the harvest once and for all. It is here that they first learn about the Breakers, although they lack a clear idea of what they do and why.
The Dark Tower
In the final novel of the series, Roland's ka-tet are brought to Algul Siendo with the help of Sheemie Ruiz and Ted Brautigan. They then face an intense battle as they fight to save the remaining Beams before the universe is destroyed.