The strange shadow floating over Riddleport has attracted a great deal of scholarly interest and research. Through this study and not a little experimentation, some information has been gleaned.
The darkness in the sky over Riddleport is known locally as Blakely's Shadow, or simply the Blot.
The Blot first appeared over Riddleport about a month ago and has remained in the sky ever since. It has changed size and shape and has even disappeared intermittently, but has always returned after several hours.
The overlord has offered a 500 gp reward to anyone who can determine what the Blot is and if it poses a threat to the city. Many have undertaken the challenge but so far there have been no results.
Riddleport has a long history of mysterious phenomena connected to its infamous Cyphergate Riddle-the long-sought hidden purpose of the stone arch that rises over the harbor. Old accounts tell of strange lights moving in the sky and sounds issuing forth from it without explanation. The manifestation of a shadow in the sky is something new, though.
No known magical traditions explain the existence of the hovering shadow, and it does not bear the trappings of any known spell.
The wizard Argentus Blakely (a noted Cyphergate scholar) postulated that the Blot is some sort of convergence for focusing arcane energies. He has yet to prove his hypothesis but is running several experiments to test its validity.
A local cyphermage and stargazer named Argentus Blakely first noticed the Blot before it was visible to the naked eye. He called it an "atmospheric shadow" and it was subsequently named for him as it became more visible.
Blakely flew up to investigate the eerie shadowy Blot a week after it appeared, and reported that the interior was strangely cold but that the blot itself seemed no different than a regular cloud-apart from its unusual color.
Blakely's been out of town recently, on a long journey to Magnimar and thence to Korvosa to research the Blot in the libraries there. In his absence, the Order of Cyphers has been leading the charge on additional localized investigations of the Blot.
The Blot has no known analogy in nature.
Birds and flying creatures appear to avoid the air space around the Blot. Although it resembles a dark cloud, the wind seems to have no real affect on it.
The Blot changes shape and size somewhat, but is generally ovoid in shape and hovers alternately over the harbor and gulf just south of Riddleport. It is dark like a shadow but does allow some light through, albeit dimly, and flying objects can faintly be seen through its obscuring haze. It casts a faint shadow on the ground beneath it depending on the angle of the sun.
The Blot hangs at a fairly constant altitude of about 2,500 feet and appears to be roughly 250 feet long by 130 feet wide.
The Blot seems to move in a pattern that appears erratic until studied closely. It follows an elliptical orbit traveling north over the town and south over the gulf, shifting north and south as the tides shift. It is closest to Riddleport at high tide.