It is a magical bug, that will allow the owner to hear what is said in the immediate vicinity of the “bug.”
Once two or more matching helms are found and worn, they enable the individuals to communicate like they were standing next to each other. The helms transmit all sounds including the surrounding noise and at the same volume as the original.
Itching dust makes someone or something itch. It is very distracting and only gets worse until the dust wears out or an antidote is applied.
Wearer of this shirt can walk unnoticed into almost any even/gathering/bank and perform just about any action without being noticed. Only extremely out-of-place action will get the wearer noticed at all.
The party is walking through the forest at night when they come upon a clearing. Half a dozen black-robed corpses lie scattered across the ground, and a pentagram of blood is shoddily drawn in the dirt.
It seems these people summoned something they could not control. Whether or not the demon returns is up to the GM, but it would be just as rich if the demon never returned, and for the rest of the night, every stray sound or odd shadow will be jumped at!