Mood Ring (5e Equipment)
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Ring, uncommon (attunement required for the Bluffer's Ring feature)
A metal band encased in what appears to be glass. When worn, the glass changes colour depending on how honest the wearer acts (white = outright lying, black = honest, grey = dishonest/evasive).
Bluffer's Ring. If you spend a short or long rest attuning to an Honest Ring, you may change the colour of the ring at will. This grants you advantage on Charisma (Deception) and Charisma (Persuasion) checks against individuals who understand the basic function of Honest Rings.