They are made from mud, being born from underground pits. They keep attempting to rebuild Revendreth's dilapidated infrastructures and constructions, but it is a losing battle considering the anima drought.
All dredgers are made from muck pools using filth and fiber through an alchemic process, which are found in the Dredgewood and Muck Pool: Banewood. It seems the Blistering Bog was once a muck pool. When muck pools go untreated due to lack of filthy rubble, they begin to generate elementals.
Out of sight, out of mind, and absolutely subservient: that is the ideal dredger. For those muck-born simpletons to seek reward or appreciation for their work is a distasteful thought indeed.