Hurrum beetles are small, brightly-colored beetles used as pets in the Dark Sun setting. They produce a pleasant humming noise that renders creatures calm and easygoing.
In their original form, they are almost entirely set-dressing, with exactly one mechanical effect: a saving throw to avoid finding the humming pleasing. For our purposes, we're going to modify it a bit, so that it is a useful piece of equipment rather than a monster. Thus, your character can buy one and then make use of it.
This small, brightly-colored beetle hums pleasantly.
Equipment (1 sp): The hurrum is a small colorful beetle that constantly produces a small, pleasing hum. All Charisma checks made against those who can hear the beetle's hum gain advantage.
World: Hurrum beetles are sold by many merchant houses, and are used by many nobles as a way to keep peaceful in tense negotiations. They are common creatures that live in hot deserts.
Story: Hurrum bettles are useful for charismatic characters, such as bards or other diplomats. They often symbolize peace and nonviolence.
Mechanics: Hurrum beetles are most useful when your targets can hear them, but you cannot (inoculating you against your enemies gaining advantage), making them ideal for interrogations and negotiations.