Quote Originally Posted by boys from the dwarf
its probably a new sort of materia. after all there isnt a bahamut sin materia in the game. im sure that if you think about it the materias shown in the game arent all of the different types in the world.
Bahamut Sin is obviously new, since it wasn't in the game. Summon materia is always red. So the materia Kadaj inserted into his arm in the Forgotten City could not have been Bahamut Sin, but some other type of Support materia.