This beautiful instrument (actually a Lyre) has a deep red lacquer. It bears the symbol of goddess of night, sorcery and crossroads (e.g., Hecate). Under moonlight, or at a crossroad, the symbol glows faintly.
No matter how a performer plays, no matter what song and no matter how they tune it, every melody comes out in a minor key. Even the most jovial dance or jig transforms into a funeral dirge. No magical spell or spirit can change this strange feature.
The harp’s music has a profound effect on young men and women, warriors, magic users and those of neutral or chaotic alignment. When anyone who fits any of those descriptions hears this music, they must make a saving throw at a disadvantage or else become charmed by the instrument. The effects last until the next sunrise, but ever after the individuals think favourably of the musician and feel discomfort around holy sites except those of evil deities. While standing in such a location or when they look at a holy symbol, they suffer a penalty of -2 to Constitution and Wisdom. The effect only goes away if the victim gets as far away as possible for at least a week.
If the a person hears the instrument played three times (three songs or three encounters, whichever happens first), they will gain an insanity : Obsession with the Harp. Non-player characters affected in this way will do their best to buy, acquire or steal the Harp. Player characters will feel the same way, but are able to resist the compulsion: however, if they ever indulge in their obsession and acquire the instrument, grant them a whole level worth of experience points.
The instrument has been passed down over the years from owner to owner, each one suffering a dark fate of some kind. Anyone who claims Hecate’s Harp will find that their ultimate fate is tied to it, somehow.