Creeping Derengea, or endoflorescence terribilis, otherwise known as The Creeper or The Green Thumb, is a virus present in Advance Wars: Days of Ruin. It was originally discovered by Dr. Morris. It is a lethal virus, eventually killing off those who catch it. It causes a number of plants and other foliage to sprout on the deceased's corpses. Originally it only affected younger people; however, it later mutates and becomes strong enough to kill older people. Dr. Morris even states that the virus is not natural and may be a biological weapon. Known people infected by the virus are Lin, Isabella (later cured), the mayor, Davis, and possibly Greyfield. Many survivors and NRA soldiers faced firing squads after contracting the virus. The virus was created by Caulder. The flowers of the Creeping Derengea are seen as terrain in the 6th campaign level, Fear Experiment, as an alternate type of Plains. The effect of the virus is never seen ingame - only in cutscenes.
- The Creeper cannot survive under sunlight, and was originally dismissed as a failed experiment by Caulder. Later on, he releases the virus upon the decrepated world, taking advantage of the dust cloud covering the skies in order to study its effects on others.