Here in this step it starts to get a bit time consuming because you have a lot of detailing and definition sketching to do. Starting at the face (always start at the top), start sketching out the eyes, teeth, and all the detailing inside the mouth. Now you can sketch in the definition on the batty looking frills or ears. Sketch in the wrinkles on the upper neck and sketch in the detailing down the neck paying close attention to the ripped flesh lining in the middle of the body. Add more of the detailing along the body and move onto the wings and draw out the lining that will eventually look like an actual skin based wing.