Mordirith (Sindarin for Black-watch), the False King, is the Steward of Angmar and one of the primary antagonists of The Shadows of Angmar. While the Witch-king of Angmar is abroad to seek the One Ring, Mordirith commands the forces of Angmar in his stead. This position leads him into direct battles with the heroes of Eriador on several occasions. Most notably, he can be found as the final boss in the last room of the Castle of Carn Dûm, called the Seat of the Witch King.
Mordirith was once Eärnur, the last king of Gondor who routed the Witch-King's army at Fornost in III 1974. The Witch-king challenged him in III 2050 and Eärnur rode to Minas Morgul but was never heard from again. The Witch-king bound his spirit and gave him great power, making him Steward of Angmar and the Witch-king's most faithful servant.
After his defeat at the hands of Narmeleth, Mordirith is sent back to Minas Morgul, receiving yet another, stronger body from his master. He now leads the Morgul-host in the conquest of Osgiliath and the siege of Minas Tirith under a new name - Gothmog (Sindarin for Oppressive Dread), the Dread Terror of Minas Morgul.
After his defeat on the Pelennor, Mordirith retreats to Minas Morgul. He fortifies his position there after the fall of Sauron and the Nazgûl, protected by the broken Gúliant and the Morgulduin to north, the Fennas Gost to the east, and the mountains of Achathras to the south and west.
Players battle against Mordirith in a number of forms and places. These include:
- Mordirith (The Gates of Carn Dûm)
- Mordirith (Mordirith's Fall)
- Mordirith (Carn Dûm)
- Mordirith (Gador Gúlaran)
- Gothmog (Gothmog Appears)
- Gothmog (The Darkest Hour)
- Gothmog (Throne of the Dread Terror)
- Gothmog (On a Field of Red)
- Gothmog (Gothmog's Rage)
-  Volume I, Book 7, Instance: The Gates of Carn Dûm
-  Volume I, Book 8, Instance: Mordirith's Fall
-  Volume I, Book 11, Instance: Prisoner of the Free Peoples - Solo-only
-  Volume I, Book 14, Instance: The Doom of the North
-  Volume I, Book 15, Instance: One Hope Remains
-  The Battle of Rhunendin - Fellowship
-  Volume IV, Book 3, Instance: Gothmog Appears
-  Volume IV, Book 6, Instance: On a Field of Red
-  The Black Book of Mordor, Chapter 14.2, Instance: Gothmog's Rage
-  The Black Book of Mordor, Chapter 14.3, A Casket of Dust
-  The Black Book of Mordor, Chapter 14.4, Instance: A Vengeful Heart
-  The Black Book of Mordor, Chapter 14.5, A Final Escape
In addition, the player visually remembers Mordirith in:
-  Volume III, Book 6, Instance: Troubled Dreams - Solo-only
-  Volume III, Book 7, Instance: A Journey by Boat - Solo-only
Eärnur also appears in a number of flashbacks in the Black Book of Mordor:
-  The Black Book of Mordor, Chapter 13.3, Instance: The Picture Painted
-  The Black Book of Mordor, Chapter 13.6, Instance: The Sword and the Stonemaiden
-  The Black Book of Mordor, Chapter 13.9, Instance: The Warrior Remade
-  The Black Book of Mordor Epilogue, Instance: Vóin's Tale
-  The Black Book of Mordor Epilogue, Instance: Freed of the Burden
- "Let us put it to the test and see who is the stronger!"
- "I would not thought it possible that you could challenge me for so long..."
- "Let our battle be at its end!"
- "I am Gothmog, the Dread Terror, and Minas Tirith shall crumble before me!"