The Monestary Sentinels are the first boss in child of light. They are two gargoyles who are sworn to protect the queen of the night. To activate this boss you must do a light puzzle. There are 3 colorful lamps which Aurora must light. You must match the colors. However there can only be one color a use. So you must flip a valve in order to change them. Upon activating the first 3 the boss is activated. 

This boss is completely vulnerable to light.  They are depicted as tall slender Romanesque statues with long horns for a weapon. They also have wings and hold their heads with their hands.