Bone Crusher

In the early days of Pagan, Lithos, Titan of Earth, wanted the people of Tenebrae to worship him. The problem was that they already worshiped Hydros, Titan of Water. Enraged over this, he sent his undead army to destroy the city. Lord Elsmil the Tempest received Bonecrusher from Hydros, a hammer that could smite the undead. The army was destroyed in battle, and Lord Elsmil killed, but the Bonecrusher vanished. Until this day, the Bonecrusher hasn't appeared again.

Following a lead, the Avatar found a cave on the Plateau, where the hero found the legendary Bonecrusher, guarded by Invisible Stalkers. With this weapon, it was easy to overcome Lithos' undead creatures. It is unknown what happened to it after the Avatar left Pagan for Britannia.

Lore
''And so it was in the early days of Pagan that the Titan of Earth, Lithos, declared that all who lived upon his lands should pay homage to him. With his mighty earthquakes, he demanded that the people of Tenebrae bow to him, lest he shake their houses down around them."But mighty Lithos," said the Lord Elsmil, the Tempest, "we are under the guidance of Hydros. From her we receive the rain for the crops and the fish for our table. We can not bow to you." This greatly angered Lithos and to punish the people of Tenebrae, he sent a great army of undead skeletons to slaughter them. Lord Elsmil, went to Hydros.''

''"Please," he begged her. "The people of your city are being slain by the minions of your brother, Lithos. We must have your help." Hydros heard the plea of her Tempest and gave to him a mighty hammer. "You shall have this weapon called Bone Crusher and with it defeat the minions of Lithos." she said. When Lord Elsmil arrived back at the battle, it was going poorly for the Tenebraens. They were fighting bravely, but were outnumbered two to one by the undead. Lord Elsmil let out a mighty roar and waded into the carnage wielding the mighty Bone Crusher. The skeletons fell before him like trees and the tide of the battle was turned. By evening the last of the skeletons were being hunted down in the woods and the town of Tenebrae was saved.''

''However, Lord Elsmil was missing. The Tenebraens began to look for him. They finally found his crushed body on the battle field, but the wonderous Bone Crusher was nowhere to bee seen.They looked for it for many days and nights, but did not find it. Though several of the searchers found the prints of bony feet in the soft dirt of the western forest. By the looks of the prints, they said, the skeletons were dragging something heavy behind them. A few of the searchers even say they caught a glimpse of bony white and the glint of light off something gold. To this day, intrepid treasure hunters continue to look for the hammer called Bone Crusher.''

-from "The Saga of Bonecrusher", Ultima VIII

Trivia

 * Bonecrusher is the strongest magic weapon in Ultima VIII. Its bonus is double the damage against the undead creatures (good, because there are a LOT of undead walking around).