The Platinum Ageis

The goddess Tiamat gazed down upon the massive army before her, all gathered to try and send her back to the realm of the gods. There, in the sky, racing towards her was a flight of the meddling metallic dragons. At the head of the formation, none other than Bahamuts chosen, the massive silver Dragonborn, Saba Azzadus, riding atop Biendysdor the Ancient, oldest of the metallic dragons. The ferocious goddess inhaled from all five of her heads, so strong was her intake of breath that anything nearby was sucked into one of her maws, as each one turned towards the incoming dragonflight, she let loose a powerful breath weapon from each of her heads. The raw power of each blast combining together to form one massive beam of elemental energy, surely dooming the goodly dragons racing towards her.
Upon her perch on the back of Biendysdor the Ancient, Saba Azzadus stands, digging her foot claws into the dragons neck. It was at last time to use the gift her god has bestowed upon her. Reaching back, she pulls forth the massive shield on her back, a large platinum scale, it's brilliance shining brighter than the coming beam of deadly elemental energy. Steeling herself, Saba tightens the straps and slams her foot down twice, giving the sign to Biend to launch her from his back. And so Magical Shield meets the breath weapon of a goddess....
...it was said that resulting impact knocked all those in combat to the ground. Then while looking up into the sky, the soldiers were in shock, watching the elemental beam that was surely going to end their great champion be turned back towards the wicked goddess. Those that had managed to regain their feet were once again knocked to the floor as the blast of Tiamat's own energy cleaved into her many heads, sending the massive dragon goddess tumbling to the floor.
It was said that The Platinum Aegis was the turning point for that battle, and the one reason the forces of good were able to prevail that day. The Aegis intercepted many a blast from the goddess, always sending them ricocheting away, or back at the five headed dragon. By the end of the battle, when the goodly dragons and mages of the North had once again bound Tiamat and sent her back to her godly realm, the Platinum Aegis was said to have been ripped asunder.
No one knows what had happened to the pieces of the Aegis...some say there were two pieces, or as many as five, but every young dragonborn is told the story with the hopes of one day finding and restoring this artifact to its former glory.