This category refers to any Ultra Kaiju in the series Ultraman X, whom were struck by the mysterious Dark Thunder Energy, thus becoming violent and brutish as a result (in certain cases, their power only increase, though lacking aesthetic changes). Some of them were unwilling victims, though there were those whom willingly bathed under this energy in hopes of harvesting its power. Victims usually display a pair of bright red eyes to indicate the dark energy's presence within their body.