Tiamat and Bahamut
The same edition of Dungeons & Dragons that introduced Bahamut also introduced his antithesis. This opposite was named Tiamat, the Chromatic Dragon and Queen of Evil Dragons, as well as the mother and deity of all evil dragons. This pairing features prominently in the deity lore of the game, with Tiamat even being featured in the television cartoon adaptation of the game.
This pairing of Tiamat and Bahamut as the antithesis of each other has since recurred in other fantasy settings. In both the original Final Fantasy and Final Fantasy VIII, Bahamut is portrayed as benevolent, while Tiamat is portrayed as malevolent, keeping close to their origins in D&D.
Both also occur in the card game Three-Dragon Ante, and Aspects of them have been created as plastic miniatures.
Read more about this topic: Bahamut (Dungeons & Dragons)