Silent Ones were a type of troll found in Marvel comics - mainly the stories involving Thor.

When Loki attempted to set Thor against the Hulk, Thor saw through his plan and sought out Loki on the Isle of Silence. Loki summoned up one of the Silent Ones to defend him, and it grappled with Thor, but Thor drove back underground with a flash of lightning.
Years later, Loki returned to the Isle of Silence to brood over how his earlier scheme had resulted in the formation of the Avengers. The Silent Ones lay about near him, listening to his rant.
In an attempt to gain revenge upon the Avengers, Loki formed an alliance with several super-criminals, and based their meetings in the Isle of Silence. The Avengers managed to follow the Wizard to the Isle of Silence when he attended a meeting, and Loki attacked them, unleashing one of the Silent Ones against Captain America. However, the Silent One was outfought by the Captain.
Morgan Le Fay used the magic of the Norn Stones to send some of the Silent Ones to Albuquerque, New Mexico, where they attacked Firebird. Firebird unleashed her fiery powers against the Silent Ones, but they only disappeared when Morgan Le Fay teleported them away.