Glass sword

The Glass Sword is a one-handed sword, and a very mighty magical weapon, capable of killing any enemy with a single strike. However, the very nature of this sword is also its greatest disadvantage. After the glass breaks and the magic kills the enemy, the sword is useless and can only be thrown away. Therefore, adventurers keep them for especially dangerous foes. Due to their nature, Glass Swords are light in weight.

According to Vetron's Guide to Weapons and Armour, the Glass Sword has an effectiveness rating of 127, compared with 90 for a Cannon. While the Black Sword can also kill in a single strike, Vetron lists its power as "unknown".

History
Glass Swords first appeared in Ultima V, in the same location of the Serpent's Spine where the White Stone was found in Ultima IV. The party could possess up to six at a time, reappearing in the same spot only after the old swords were used up.

In Ultima VI, Glass Swords could be found as loot, or could be made by a glassmaker in Minoc, who demanded Peer Gems and money for his work. A Glass Sword was needed to make the Britannian Codex lens.

In Ultima VII a Glass Sword was a rare find; one could be found in a pirate treasure in the Cape of Heroes.

In VII/2, the Avatar was given a Glass Sword before setting out to Serpent Isle, but it was lost almost instantly upon arrival in a Teleport Storm; it was eventually found by Hazard the Trapper. Glass Swords were also sold by Pothos of Moonshade, for 1500 Guilders each.

Glass swords could also be found in Ultima IX, but they were weaker -- some enemies could survive a single strike.

Trivia

 * In Ultima VI, Glass Swords were useful for destroying doors as well as killing monsters, though sometimes you had to use more than one.