That was the Ghost of the Grave.

My grandfather met him ere he came to his end in the forest, none know how, for the wolves, of which there were plenty in his day, picked his bones clean, and so have many others for hundreds of years; always just before their doom.

He is an ill fowl, that Ghost of the Grave, and those who clap eyes on him do wisely to turn their horses' heads homewards, as I would to-night if I had my way, master." "What use, Jeffrey?
If the sight of him means death, death will come.
Moreover, I believe nothing of the tale.

Your ghost was some forest reeve or herdsman." "A forest reeve or herdsman who wanders about in a steel helm on a fine horse in snow-time when there are no trees to cut or cattle to mind! Well, have it as you will, master; only God save me from such reeves and herdmen, for I think they hail from hell." "Then he was a spy watching whither we go," answered Sir John angrily.
"If so, who sent him?
The Abbot of Blossholme?
In that case I would sooner meet the devil, for this means mischief.

I say that we had better ride back to Shefton." "Then do so, Jeffrey, if you are scared, and I will go on alone, who, being on an honest business, fear not Satan or an abbot, either." "Nay, master.