Twisted Times in Twinsmouth

Who is the mysterious and powerful lord who asked E. A. Poe to come to his house a few days before he died? Is he the same person who, almost a century later, would send a similar invitation to H.P. Lovecraft?

And how do two small towns founded by twin brothers on either side of a small stream relate to all these events?

A mistake made in grief may have unleashed something that should never have come ashore.