Brass Men are one of the two versions of "good" undeath. If the proper spell is cast to preserve bits of a dead(normally, warrior) the person can live on. A brass clockwork body is made and parts of the corpse are used to animate it. Normally the brain, one ear and one eye are all that is needed to bring the person back to a state of unlife. The brain is perfectly preserved and the brass man is free willed. Usually the lack of hormones gives the brass man a "flatter" personality in undeath. Arms and legs are not used as the brass body is far more durable.
Immortality can be achieved in many ways, freetext Friday "robot"