More information on this subject would be appreciated, I can't find any online, so this is strictly what I know...

Gargoyles are creatures of the night that are often found on old castles and buildings of the midlevel times. These gargoyles are said to come to life to protect the inhabitance of the castle they live on. During the day they 'sleep' atop the buildings. It depending on the myth, they can come to life during the day if the need to, although some say they can only transform at night.
Gargoyles can often use their wings to fly or to glide. Some tales tell that they turn into humans during the day, or at will, and the reason for the stone gargoyles on buildings is to create hiding places for them when they are in gargoyle form.
Some theories suggest that gargoyles are acutely a sub-species of vampire, usually cast as the servants and guards. In this manner, they would guard vampires during they day when they are at their most vulnerable.