The Underworld is an alliance of supernatural villains who work together to further the cause of their dark masters.
The earliest version of The Underworld was formed by She Devil and Death's Chaplain, the two of them agreeing to aid each other to fulfil their own goals, as well as the goals of their demonic masters. To this end, they recruited similar villains, ones whose powers had been derived from supernatural or mystic sources. While obstinately all were equal in the group, it was clear that She Devil was in complete control of the organization, with Death’s Chaplain her second; all others were considered to be their minions.
In spite of the power of this group and their sinister overtones, their actual abilities would prove to be somewhat lacking; the group were often easily defeated in battle; while having their heads handed to them by superteams was common place, they also had been known to be defeated by individuals, despite their numerical advantage. One of their number, Droch, went on record as having been defeated in seven seconds in a single battle.
The net result is that the Underworld’s most common recurring supercrime is breaking its other members out of jail.
Membership is open to any villain who derives their abilities from a mystical or supernatural source, specifically one of a dark origin. Aside from that, the only real requirement is a willingness to do whatever She Devil says.