Not a team per-se, but a pool of solo criminals, thugs and masterminds which do team-up on a case by case basis or as fate throws them together. This pool of solo-criminals has no underlying organizational structure, leadership, or stated goals. The only actual requirement for joining is that the character be considered a villain, some character who performs actions which create opportunities for themselves with a general disregard for others. While the members in this group may know each other and in some cases work together, these unions are based on fate or personal choice, not their membership in the team. This team acts as the de-facto affiliation of a villain who, for whatever reason, does not fit or chooses not to be in a structured team. Their alignment can span the gambit of all evil attributions (lawful, chaotic, or neutral) and even move into areas of abstract neutrality (lawful, chaotic or neutral).
Solo Villains share a hearty and well earned distrust for their fellows in crime. As such it is unremarkable so many villains walk the path of crime alone. The big downside is that heroes generally have no such aversion to working with their own which leads to being outnumbered. For these reasons a loose network of villains developed where help can be found for profitable operations.