Harbinger's Lute

An unassuming whistle made of what seems to be ivory or yew with small metal detailings. It makes no sound. Or at least it makes a sound too high a frequency for even elves to pick up on. All monsters, fiends, and aberrations within a 3-mile radius will converge upon the area from which the whistle sounded with startling accuracy. They are not by any means bound to the whistleblower's will or wishes, much less their well-being.