Gwani Horn - from "Balancing the Scales"
The Gwani Horn has the same effects as the Horn of Praecor Loth, albeit because of it being much smaller, its powers are also more limited, as it can only smash blocks of ice instead of shattering buildings.
The Gwani of the Serpent Isle had this Horn for generations, until Vasculio stole it, knowing of its powers. He put the horn into a force field in his base in Skullcrusher, so that his prize wouldn't be stolen by anyone. The Avatar got the Horn in Ultima VII Part Two, after finally getting the Dispel Field-spell, and used the horn to free Gwenno's body from an ice block in the Gwani's cemetery, so that she could be resurrected.