A-47, also known as "The Shark-Toothed Janitor," is an entity that resides in the Rooms. He earns his nickname from cleaning and having sharp teeth. He starts at A-0 and rushes forward to the next unopened door. He speeds up the farther he goes into the Rooms. Upon reaching the current room, he will check all hiding spots, disintegrating anyone in sight, eventually disappearing without a trace. It is still unknown where he goes when he vanishes.
Fun fact: From the information that A-47 has given, he was a former janitor named Franklin Benjamin Jandston, who worked in the Alpha Section. He says his boss took part in a tragic work accident resulting in his untimely demise. How he became an entity is unknown.