Blackstone

A blackstone on a silver chain is an object that makes it possible to travel to someone elses dream. Worn around the dreamers neck for a few nights it gives them the ability to see someone in their dreams and speak to them.

Continuity
Malcolm offers Andy a thousand dollars to spy on the Traveling Salesman and Amanda. This happens between episodes, however Andy talks about it in Voicemails From Darkness - MSG 5: Dreaming Wrong.