Sword of Stone Strike

The Sword of Stone Strike is an enchanted sword which paralyzes those it strikes. It appears in  Ultima Underworld II.

Description
The Sword of Stone Strike belonged to a warrior who sought to penetrate the depths of the Tomb of Praecor Loth. In exploring the initial level of the crypts, she encountered a demi-dragon and was drawn into a battle that saw them both slain. Later, should the Avatar happen upon the blade, they could take it for their own, and would discover that the sword had the unique property of rendering any living thing it struck temporarily motionless. This made it an invaluable weapon to a skilled swordsman, although it -ironically- would do little to assist the hero in dispatching the undead denizens of Loth's tomb.

Ultima V: Lazarus
In Ultima V: Lazarus, the Sword of Stone Strike can be acquired from Nilrem of The Herbalist for rescuing his injured owl Sedemichra.

Trivia

 * Getting this weapon before fighting Dorstag (by opening the way to Rhiannon) makes the battle against him a complete joke.
 * The sword also makes both battles against Mors Gotha a breeze, as she can't defend herself once paralyzed.