Great Beasts of Burden
“Grond they named it, in memory of the Hammer of the Underworld of old.
Great beasts drew it, Orcs surrounded it, and behind walked mountain-trolls to wield it.”
LOTR: ROTK B5 C4
Little is known about these beasts of burden. They were first seen in the War of the Ring at the Battle of the Minas Tirith, upon the burning plain of the Pelennor during the siege of the white city. They are mentioned only in passing in the Red Book of Westmarch, which unfortunately is one of the few remaining written accounts of the battle. They must have been mammoth in size in order to pull the engines of war made by Sauron within the walls of Mordor. They were called ‘Great Beasts’ for they were charged with hauling many of the siege towers and engines of war across the burning field of battle, but it was the hauling of the vast battering ram Grond for which they are truly remembered.
Some believe the these great beasts or ‘Siege Beasts’ were simply one of the many Mumakil used in battle, however there are accounts that state that these creatures that came out of Mordor, were in fact another form of beast altogether. It is believed the they like the Mumakil, were found deep in the jungles of Far Harad and brought north to Mordor, where they were bred with other foul creatures in the pits of Barad-dûr using dark sorcery to make them stronger, larger and more deadly in battle. They wore no armor, because their hides were thick and they had a great horn upon their heads.
These creatures, which are named in the Book of Fire as ‘Siege Beasts,’ though little was written about them. It is said they come from a long line of brutes of ancient origin, that had existed in the wild lands of the far south for time immemorial and that Sauron made of them brazen beasts for use in battle. What foul craft was used to breed these creatures is not known, for none now live who remember it. No account is written about these great beasts, that could be found even in the Library of Shadow.
Ever since the middle night the great assault had gone on. The drums rolled. To the north and to the south company upon company of the enemy pressed to the walls. There came great beasts, like moving houses in the red and fitful light, the mûmakil of the Harad dragging through the lanes amid the fires huge towers and engines. Yet their Captain cared not greatly what they did or how many might be slain: their purpose was only to test the strength of the defense and to keep the men of Gondor busy in many places. It was against the Gate that he would throw his heaviest weight. Very strong it might be, wrought of steel and iron, and guarded with towers and bastions of indomitable stone, yet it was the key, the weakest point in all that high and impenetrable wall.
The drums rolled louder. Fires leaped up. Great engines crawled across the field; and in the midst was a huge ram, great as a forest-tree a hundred feet in length, swinging on mighty chains. Long had it been forging in the dark smithies of Mordor, and its hideous head, founded of black steel, was shaped in the likeness of a ravening wolf; on it spells of ruin lay. Grond they named it, in memory of the Hammer of the Underworld of old. Great beasts drew it, Orcs surrounded it, and behind walked mountain-trolls to wield it.
But about the Gate resistance still was stout, and there the knights of Dol Amroth and the hardiest of the garrison stood at bay. Shot and dart fell thick; siege-towers crashed or blazed suddenly like torches. All before the walls on either side of the Gate the ground was choked with wreck and with bodies of the slain; yet still driven as by a madness more and more came up.
Grond crawled on. Upon its housing no fire would catch; and though now and again some great beast that hauled it would go mad and spread stamping ruin among the orcs innumerable that guarded it, their bodies were cast aside from its path and others took their place.
Grond crawled on. The drums rolled wildly. Over the hills of slain a hideous shape appeared: a horseman, tall, hooded, cloaked in black. Slowly, trampling the fallen, he rode forth, heeding no longer any dart. He halted and held up a long pale sword. And as he did so a great fear fell on all, defender and foe alike; and the hands of men drooped to their sides, and no bow sang. For a moment all was still.
From The Lord of the Rings: The Return of the King in the chapter ‘The Siege of Gondor’