Curse of Strahd
The Sword of Khellig
The Sword of Khellig is a powerful weapon once wielded by a barbarian lord of the same name. Khellig opposed Strahd in battle, which led to his death and the doom of his whole tribe. The sword was lost on the battlefield but was somehow recovered by the Vistani.
The Sword of Khellig is a +1 greatsword that appears to be made of clear glass. The bearer can use an action to make his voice carry clearly for up to 300 ft away, without shouting. The bearer of the weapon is suffused with feelings of self-confidence. Further, it glows in the presence of demons.
Update As the wielder of the blade becomes more powerful, so too does the Sword of Khellig. It is now a +2 greatsword.