Grond (battering-ram)
From Tolkien Gateway
The battering-ram Grond, as portrayed in Peter Jackson's The Return of the King
Grond was a battering ram, used to destroy the Great Gate of Minas Tirith during the Battle of the Pelennor Fields. It was named intentionally to evoke the memory of the ancient weapon of Morgoth, the "Hammer of the Underworld".
