Tiamat

Tiamat (pronounced: /ˈtiɑːmɑːt/ TEE-a-mat[17] or: /ˈtiɑːmɑːt/ TEE-a-maht[10] ) was the lawful evil dragon goddess of greed, queen of evil dragons and, for a time, a reluctant servant of the greater gods Bane[18] and later Asmodeus.[19] Before entering the Faerûnian pantheon, she was a member of the Draconic pantheon,[6] and for some time she was also a member of the Untheric pantheon.[7]

Tiamat was also the eternal rival of her brother Bahamut, ruler of the good metallic dragons.