Psi Crystal

From Icewind Dale: Rime of the Frostmaiden, page 315.

Description
Wondrous item, uncommon (requires attunement by a creature with an Intelligence score of 3 or higher).

This crystal grants you telepathy for as long as you remain attuned to it. The crystal also glows with a purplish inner light while you are attuned to it. The higher your intelligence, the greater the light's intensity and the greater range of the telepathy (see the Psi Crystal Properties table).