I actually thought it would too! Why I mentioned it.
However, someone recently told me about this item
which I think also drops from Dreadtooth. Does someone want to try having the mask on and the amulet in their inventory? It is a use item so maybe using it in the cave when you have the mask on does something?
I don't know about Dreadtooth dropping it, it was datamined. And when I read the "use", it sounds more like a social item.
I could imagine someone going in the cave with the mask on, and using the amulet on his group to make them scream.
Curiouser and curiouser. We must get to the bottom of this, Watson!