Common Knowledge and rumors you have heard about “The Gray”-
They are subterranean dwelling goblinoids. Emperor Daldoth would have liked to have wiped them out during the great war that drove out the dragonborn, but his human armies were not well suited to combat in the underdark, and the Gray cities are very deep under ground.
Supposedly they will kidnap and enslave bad little kids, sometimes adults. You’d like to think that these were just stories told to frighten children, but you seem to remember some actual cases of friends going missing and being told they were taken by the Gray.
A Gray is said to be as strong as three normal men. It’s known that some use magic, many use poison.
You’ve heard a rumor that the bite of a Gray, if untreated, can become infected and turn a man into a Gray. It has to just be a silly rumor of course, such things can’t actually happen, right?
Commonly work with “Graylings” smaller goblinoids that are not as strong or fierce in battle, but very quick, sneaky and supposedly some can turn invisible.