The Bright Blade was a unique crystalline longsword that belonged to Saint Alizandra Markovia, before being passed down to her disciple Sergei von Zarovich. The weapon was shattered in a battle with Sergei's brother Strahd von Zarovich, and cast aside to the wilds of Barovia. However, while the blade's physical form was lost, a strange sentience developed within it. What remained was the hilt, which still contained the sword’s radiant spirit, and became known as the "Sunsword".
This fragment of the original weapon maintained a purpose: to destroy the undead and bring light to the darkness of Barovia. Though incomplete, the hilt could be reawakened by a worthy bearer of law and goodness, at which point it projected a brilliant Sun Blade. Fueled by devotion and lingering memory of its master, the Sunsword maintained a limited intelligence and could communicate with an attuned creature through empathetic feeling.