Had the same reoccurring nightmare every night for the best part of 6 years - the nice thing is i could use it as a trigger for lucid dreaming

My dream would start with me lying in bed with me unable to sleep - as i looked upwards i'd notice the room getting darker as a shadow was cast across the room as the light from the window was obscured , i'd hear the usual clunk-clunk-clunk of metal
This :

would be standing outside my window
there'd be an age as i would get out of bed and walk towards the curtains to open them to reveal it there - it would prime itself to blow me away and i'd run screaming for the door - sometimes it would open, sometimes there'd be no knob on the door.