The Weird of Crystal is an artifact featured in He-Man and the Masters of the Universe.
The Weird of Crystal was a very dangerous, rare and ancient crystal, that turns living beings into crystal. The only known cure was stored within the knowledge of Granamyr.
Skeletor, disguised as Ambassador Therin of Eastfen, attempted to trick King Randor into touching the crystal, magically fused with a jade statue. Man-At-Arms realizes that Ambassador Therin was actually Skeletor and grabbed it before the king and became crystallized instead. He-Man and Teela travelled to Darksmoke to find a cure for Man-At-Arms.