This is the nightmare that haunted me for years as a child. I had a fear that I would wake up to death coming after me.
I had it pictured like this too, silent and making the air cold as this neutral, hidden face came closer. I could only ever see his hands (one on the door, opening it and the other holding the large scythe) which were white, bone made a dull gray over time. His cloak always hung with all these folds of shadows as if he was almost just made of a living material.
I drew my actual door way and used the molding that is actually in my bedroom as a reference on that part. That box you see in the closet behind him? Used to sit right there. This image still kind of terrifies me.