The ring of charos is an item found after Creature of Fenkenstrain by pickpocketing Dr. Fenkenstrain. The ring was once owned by a human named Charos, whose gift of speech allowed him to bend the wills of the weak-minded. He was aided by his magical ring.
The ring can be activated at the start of the Garden of Tranquillity quest, after completing the Wise Old Man's quiz on persuasion, becoming a Ring of charos (a). The activated ring's persuasive abilities are used in several quests, including Do No Evil and While Guthix Sleeps. After being activated, the ring will stay activated even when lost.