Stave 4

I would have to say the Grim Reaper. 

The upper portion of the garment was contracted for an instant in its folds, as if the Spirit had inclined its head. That was the only answer he received.

Although well used to ghostly company by this time, Scrooge feared the silent shape so much that his legs trembled beneath him, and he found that he could hardly stand when he prepared to follow it. The Spirit pauses a moment, as observing his condition, and giving him time to recover.

But Scrooge was all the worse for this. It thrilled him with a vague uncertain horror, to know that behind the dusky shroud there were ghostly eyes intently fixed upon him, while he, though he stretched his own to the utmost, could see nothing but a spectral hand and one great heap of black.