Grendel was the name of this grim demon haunting the marches, marauding round the heath and the desolate fens; he had dwelt for a time in misery among the banished monsters, Cain’s clan, whom the Creator had outlawed and condemned as outcasts. For the killing of Abel the Eternal Lord had exacted a price:
"Along the skirts of the Dead Marshes I followed it, and then I had him. Lurking by a stagnant mere, peering in the water as the dark eve fell, I caught him, Gollum. He was covered with green slime."
(JRR Tolkien, "The Lord of the Rings: The Fellowship of the Ring")
