Greenstone amulet

Greenstone amulets were rare, extremely valuable magical necklaces that offered protection against a wide range of mind-controlling and physically dominating spells. They appeared as fist-sized stones, made of brittle greenstone, that shone with a radiance when activated. The stones were often carved into flattened versions of common shapes such as an egg, shield or simple helm.

Powers
When worn against the skin, these amulets provided a continuous mind blank spell and shielded its wearer with a spell immunity-like affect, which granted absolute protection from the spells chaos, geas, hold person, hypnotism, mass charm, mind blank, quest, score, and sleep. It also offered more-limited protection against fumble, maze, Otto's irresistible dance, ray of enfeeblement, and trip, as well as necromantic spells, dimensional transportation, and certain psionic abilities.

Greenstone amulets could only protect the wearer from a certain number and intensity of spells before it was completely drained, after which it shone extremely brightly and then slowly faded to a dark hue. It would slowly recharge after this occurrence.

Appearances

 * Video games
 * Baldur's Gate: Tales of the Sword Coast