A black virus type version of WarGreymon created by Arukenimon by fusing together 100 Dark Towers (Control Spires). Even though he contains the virus, he only fights for his personal protection and justice.
Black WarGreymon is a Mega level digimon, making it a very powerful foe to the digi-destined. He is built the excat same way as WarGreymon, except that he draws a lot of his power from more negative eneregies. Even though it is feared for the virus that it contains, the Black WarGreymon doesn't always act evil and spiteful. Usually, he lives for his own personal justice and protection, even though he isn't the nicest digimon walking around. Another difference between Black WarGreymon and WarGreymon is that Black WarGreymon doesn't have the crest of courage of it's "Brave Shield" on its back, symbolizing its a different "species" with different motives.
Black WarGreymon when angered can become a very powerful foe indeed. One of the most deadly attacks he has is Terra Destroyer. This attack in particular gives Black WarGreymon his Mega level Digimon status. Terra Destroyer takes all the negative emotions and energies in the world, and focuses this energy on a spot. That spot being the opponent or foe he is trying to defeat. Another deadly attack is the Black Tornado, or a massive whirlwind of bad energies, also known as Great Tornado.