Well I stayed there for a good few minutes, so it couldn't have been Rube, and quoins don't show on the mini map, also the other player beside me couldn't see anything so for some reason only I could see it....
At least Lord Bacon-o has encountered it before. :o)
*queue eeerie music*
I ran into one of those in Jal today. I spent a couple of minutes jumping over it to see if it did anything. I was about to ask if anyone else could see it...but sometimes I don't like to talk in crowds.