Dark Spirals

The Dark Spirals are more powerful versions of the  Dark Rings, created by the  Digimon Emperor, which run on their own independent power source and do not need the Control Spires to power them. After his experience with  SkullGreymon, the Emperor realised that Dark Rings were not powerful enough to control  Ultimate  level Digimon, and so created the Dark Spirals for that purpose. Agumon, held captive by the Emperor, had a Spiral attached to him, and was then  Dark Digivolved  into a viral version of  MetalGreymon  by the Emperor's  D-3. This Spiral was destroyed by  Raidramon, and so the Emperor developed a more powerful version, which was then seen to be used on  Gorillamon ,  Digitamamon ,  Ninjamon ,  ShogunGekomon ,  MegaSeadramon  and  Dokugumon. The  "Scubamon"  in the  World of Darkness  were seen to have Dark Spirals attached to them, but apparently they were not real, and were merely used to dupe Kari  into helping them so they could capture her. Dark Spirals first appear in "The Captive Digimon."