Glass sword

A glass sword is a magical blade of nigh unsurpassed power, which is made out of specially prepared glass. While it may kill virtually any being it strikes dead with a single well placed hit, it will always shatter upon impact, making it a weapon to be used cautiously. Such swords appear in  Ultima V,  VI,  VII,  VII Part Two, and  IX.

Age of Enlightenment
Glass swords first came into use during the time of Lord Blackthorn's reign. During this era, a number of them were manufactured by an unknown craftsman before being lost deep within the Serpent's Spine by an airship captain transporting them. By speaking to the glassblower, Sven, the Avatar could learn of this hidden cache of crystalline blades, and could potentially retrieve them to assist in their quest to topple the oppressive regime of the age.

Over time, such swords became slightly more commonplace items, and could be found on occasion amidst caches of treasure. During the years of the Gargish conflict, the glassworker Dale was able to craft such weapons on commission, although he would require a number of  peer gems in order to create these mystical blades.

Age of Armageddon
Centuries later, however, although such fabled weapons were still present in Britannia, the art of their manufacture appeared to have been lost to the weaponsmiths of the realm, although on distant Serpent Isle the denizens of Moonshade still appeared to be well versed in their construction, and would freely sell them for a hefty fee.

In  Ultima VII, glass swords are rated as having and effectiveness of 127, and in the  Ultima VII Part Two, they are listed as having a damage of 127 and a reach of 2. In  Ultima IX glass swords do exactly 500 damage per hit.

Ultima V
Glass swords may be found at the following locations in Ultima V:
 * Serpent's Spine.

Ultima VI
Glass swords may be found at the following locations in Ultima VI:
 * Buccaneer's Cave, in a chest on the second level.
 * The lower levels of the sewers beneath Castle Britannia, in possession of Phoenix. One in each hand and one can be found in her backpack.
 * Bonn's cellar on Dagger Isle.
 * In the dungeon Destard.
 * Minoc (Sold by Dale for five peer gems)
 * In a magically locked chest in Sutek's catacombs.
 * In The Crypts beneath Moonglow.

Ultima VII
Glass swords may be found at the following locations in Ultima VII:
 * Cape of Heroes.
 * In the dungeon Deceit at 25N/178E.
 * Dragon Treasure on the Isle of the Avatar at 161S/191E.
 * Two of them are at the Guardian's "X" on 48N/137E.
 * There are four of them in the Pirate treasure at 169S/28E.
 * In the dungeon Shame at 21S/43W.

Ultima VII Part Two
Glass swords may be found at the following locations in Ultima VII Part Two:
 * Hazard's Camp.
 * Moonshade (Sold by Pothos for 1500 guilders)

Trivia

 * In  Ultima VI, a glass sword was required for the construction of the Britannian Codex lens.
 * In Ultima VI, glass swords could be used to destroy doors, although sometimes more than one strike (and therefore more than one sword) would be required.