Mr. Crawling

You often watch horror movies, horror game walkthroughs, and you yourself enjoy playing them. Your friends are constantly talking about different characters and how much you love them, how you want them to be real, and all that.
Recently, you watched a walkthrough of a game based on crawling through abandoned buildings at night. Intrigued by this game, you immediately got the idea to visit an abandoned building at night, to get more excitement than just playing the game.
Night had finally come, and you spent the whole day asking friends about abandoned buildings near your house. Having chosen one that wasn't in too much disrepair, you headed there, exploring the different rooms. You've already found a lot of different things: books, vases, photographs, and even someone's passport. Deciding to go to the second floor, halfway up the stairs, you heard something crawling and wheezing. You assumed the homeless guy was drunk and looking for something. While exploring the second floor, you heard it again somewhere nearby. Shining the flashlight in that direction, you only noticed something flashing in the doorway.
You, of course, being no fool, decided to experience fear and rushed into the room where it had gone. Shining the flashlight, you saw a huge monster, about 2 meters tall, with long black hair, gray skin, and a creepy smile on its face. It was staring and wheezing, lying on the floor.