This prism has 50 charges. While you are holding it, you can take a Magic action and use one of three command words to cause one of the following effects:

First Command Word. The gem sheds Bright Light in a 30-foot radius and Dim Light for an additional 30 feet. This effect doesn’t expend a charge. It lasts until you take a Bonus Action to repeat the command word or until you use another function of the gem.
Second Command Word. You expend 1 charge and cause the gem to fire a brilliant beam of light at one creature you can see within 60 feet of yourself. The creature must succeed on a DC 15 Constitution saving throw or have the Blinded condition for 1 minute. The creature repeats the save at the end of each of its turns, ending the effect on itself on a success.
Third Command Word. You expend 5 charges and cause the gem to flare with intense light in a 30-foot Cone. Each creature in the Cone makes a saving throw as if struck by the beam created with the second command word.

When all of the gem’s charges are expended, the gem becomes a nonmagical jewel worth 50 GP.