Kings' tears

Kings' tears (also seen as king's tears) were extremely rare jewels unique to the Realms. They were sometimes called frozen tears or lich weepings.

Description
These rare stones were transparent, colorless, teardrop-shaped with a smooth surface, and incredibly hard. No mundane means were known that could break, chip, cut, etch, fracture, or even scuff one of these jewels&mdash;they were always found in this perfect state. A typical specimen had a base value of 5,000 gp.

Powers
Each specimen contained a sharply detailed, life-like image or scene that could be viewed by gazing deeply into the stone. Some contained an image of a person; some contained a panoramic view of a landscape or a battle in a place long forgotten or ravaged by time; and some held unfathomable dream-like scenes. What these images portrayed and what relationship they had with each other remained unknown, but sages fervently studied them.

The legend lore spell could take hours, days, or weeks to cast, but when cast in the presence (within 90 ft or 27 m) of a kings' tear, the casting time was reduced to 20 minutes and the caster was mentally granted a word or a name that was a critical clue to the person, place, or thing that was being researched. Needless to say, kings' tears were valued by sages above all other gems.

A ritual, known to only a handful of liches, archmages, and high priests, could be used to gain wisdom by the sacrifice of one of these jewels. Knowledge of this ritual was a closely guarded secret.

If enchanted correctly, a kings' tear could be magically cut into one to four gems of insight.

Legends and Rumors
Folklore suggested that these stones were the tears of long-dead necromancer kings and queens, crystallized to preserve the view of what they loved. Rumors also persisted that kings' tears were a part of the process to create a philosopher's stone and other powerful magic items.