The amulet of communication is a powerful artifact that lets players verbally
communicate with each other over any distance, using the TELL command. They
can be bought from a very few select stores in Waterdeep and around the
kingdoms. [Exactly where should be determined in-character(IC)!] Use of the
amulet requires the expenditure of some measure of concentration, and thus
stamina. The recipient of your TELL must have their amulet attuned to the
magical weave, as must you.
Note that the amulet being a verbal communication device, it is somewhere
between possible and probable that others will detect that you are using it -
though it is unlikely that they will manage to make out anything of what you
are saying.
Unless you are dead, you should not be contacting people you have not met, or
have good reason to know who they are, such as a faith manager, whom are
considered public figures in most cases.