Peter Jackson's depiction of the great beasts of the Dark Enemy.
The Great beasts were used by Sauron's armies as burden beasts, most notably during the Battle at Minas Tirith. These beasts pulled the battering ram Grond, named after the Hammer of the Underworld, to the gate of Minas Tirith to destroy the Wall's only weak-point.
Adaptations
In film, they are depicted as giant rhinoceros-like creatures with an odd horn protruding from their heads. Very, very little is actually known about these creatures.
Video games
Great Beasts are also used as cattle by Mordor orcs in The Lord of the Rings: The Battle for Middle-earth, and in The Lord of the Rings: The Battle for Middle-earth II they are used also by dwarves as burden beasts and are referred to as yurgs or subterranean yaks. In The Lord of the Rings: Conquest you can see dead great beasts on the maps: Weathertop and Pelennor Fields.
