Weight: ½ lb.
Estimated Value (Sane Cost Guide): 500 gp
DMG Value:
101 gp - 500 gp
A mind crystal contains sorcerous potential, allowing a user to apply Metamagic to a spell as you cast it. For the non-sorcerers among us, Metamagic allows you to tweak and alter a spell to better suit your needs, such as extending its duration or increasing its range. While Metamagic is a sorcerer class feature that needs sorcery points to use, mind crystals are single-use items that can be used by anyone who can cast a spell.
Dial up the damage! Make the fire storms hotter, the guiding bolts brighter, and the circles of death even deadlier. When your party is out of the way—or when your barbarian tells you to go ahead anyway—use this mind crystal to reroll up to three damage dice and unleash your fury.
Spell suggestions: blight, guiding bolt, inflict wounds, shatter
Source: Phandelver and Below: The Shattered Obelisk