This ruined fortress is located at the south-eastern corner of Nain Enidh, just where the sheltering ridges bends south for the marshes of Harloeg. These days orcs make camp in the ruins where they have formed an alliance with the Dourhands of Thandobel.
On the outside of the western wall of Ost Cyrn is an entrance to the Iorvinas dungeon, at the Orc side of the dungeon.
-  A Plague Upon Us
-  Iron-jaws
-  Man-slayers
-  Master of the Lash
-  Instance: A Champion's Courage - Champion
These deeds can be advanced by exploring Ost Cyrn:
These creatures are encountered at this location:
- Ost Cyrn once stood vigil against the Hill-men of Rhudaur and the Angmarim of the North. Now Orcs use the ruined fortress to lay siege to the barren Lone-lands. — Deed
|Settlements, Areas and Landmarks of the Lone-lands
|Areas:||Agamaur • Annunlos • Garth Agarwen • Haragmar • Harloeg • Minas Eriol • Nain Enidh • Talath Gaun • The Weather Hills|
|Settlements:||The Forsaken Inn • Ost Guruth|
|Landmarks:||Amon Ros • Barad Iachiant • Bleakrift • Candaith's Encampment • The Circle of Blood • Dol Vaeg • Echad Sûl • Eglain Camp • Garth Agarwen Gate • Glumhallow • Gondrinn • Ivar's Crypt • The Last Bridge • The Lornspan • Mitheithel • Mithrenost • Naerost • Nan Dhelu • Nindor • Ost Cyrn • Ost Haer • Ost Laden • The Outer Gates • Skirmish Camp • Spring of the Red Maid • Thandobel • Tornstones • Weatherfoot • Weathertop|
|Interiors:||Barad Dhorn • The Forsaken Inn • The Lore-tower|
|Instances:||Garth Agarwen: Arboretum • Barrows • Fortresss / Other: Stand at Amon Sûl • Inn of the Forsaken|