Bahamut and Tiamat
Io’s first child was a dragon called Vorel. Vorel’s name means “beautiful” in Draconic, for beautiful it was, perfect of scale and form. Eventually, Io picked a fight with an army of primordials, and was split in two. These two creatures are the god Bahamut, and the goddess Tiamat. Jealous of Vorel’s power and praise from the Dragons that roamed Terrus, Tiamat killed Vorel in unfair combat. Bahamut then banished Tiamat from the Astral Plane, and sent her to the Shadowfell. She then became the evil goddess she is today. Every century or so, Bahamut and Tiamat battle, usually with no clear winner.