However, with "D&D" 4th edition, the classifications were changed: chromatic dragons became not strictly evil, and metallic dragons became not necessarily good. Also, there are several new categories (although the gem dragons have not yet returned): "planar dragons" which are defined as dragons that were warped by living on a plane of existence other than the Material Plane, "catastrophe dragons", which take on the aspects of natural disasters which are chaotic evil and cause chaos for its own sake, and "scourge dragons". Chromatic dragons are presented in the "Monster Manual" and "Draconomicon: Chromatic Dragons". Metallic dragons are presented in the "Monster Manual 2" and "Draconomicon: Metallic Dragons". Catastrophe dragons are presented in "Monster Manual 3". Planar dragons have been presented in both "Draconomicon: Chromatic Dragons" and "Draconomicon: Metallic Dragons".