No, no, no, it's a kind of Magic, it's not an item, all Chosen of Mystra have the ability given to them,
"Once per hour, a Chosen of Mystra can unleash from within his or her body a beam of magical whitish flame known as
silver fire (which is also used as a general name for the overall power invested in each of her Chosen by the goddess). This beam is 5 feet wide and can be made to extend as far as 70 feet if desired. No magical or physical barrier has been discovered that can stand up against it, and the beam inflicts tremendous damage on all beings struck by it. Any nonliving object touched by the beam is utterly destroyed. An individual also can choose to expel the
silver fire in the shape of a cloud that fills a cone-shaped area 5 feet in diameter at its base, up to 70 feet long, and up to 70 feet across at its widest."
" This use of the
silver fire is extremely rare, since Mystra considers it an emergency action only."
It should also be noted that
silver fire is composed of pure
Weave magic energy, thus the clashing of
silver firewith pure
Shadow Magic will cause the multiverse to unravel itself, tearing the fabric of the world, causing huge dimensional rifts between the planes. As has happened in
Shadowdale in the Year of Wild Magic (
1372 DR), when
Elminster was fending off several invading
Shadow Princes, who were actually shadow-mattered creatures. His
silver fire did vaporize one of them, but also created a rift between
Toril and the
Nine Hells.