*Dungeons & Dragons geekiness*
Well, I'm not sure where Wizards of the Coast got this from, but in D&D, Bahamut and Tiamat are the two dragon gods. Bahamut is the good one, and Tiamat is the evil one. This is about where the connections stop; in D&D for instance, Timat's most distinguishing feature is that she has 5 heads in all the different colors.