The Necromongers are an empire that violently and forcefully follows and propagates its religion that is known as Necroism. Their intention is to convert or kill all who oppose them.
The Underverse is their promised land, something they live up to until the very end, believing that unless a person dies in due time that they will not got to the Underverse. They also believe in a philosophy that promised you to keep what you kill. Whenever they end another life, they are automatically entitled to their property and position.
Necromongers to not reproduce nor propagate life further, which is one of their reasons why they refer to all non-necros as breeders. Each one of the Necros are converts because they all did undergo the conversion to receive the mark of the Necromonger, two painful spikes stabbed into the sides of their necks, leaving visible scars. Through their conversion they learn how one pain can lessen another up to a point where nerved are numbed.