Grennokar was an Obsidian Order base and detention center located on Harkoum. The base was hidden from a view by a holographic cloak. Among those held there were criminals, dissidents and aliens. Some prisoners were executed, although others were used for hard labor. There were also Cardassian scientists based there who subjected prisoners to biogenic weapons, new surgical techniques and as test subjects for refining torture techniques. (DS9 novel: Warpath) Grennokar was abandoned after the Dominion War. It soon became Iliana Ghemor's base of operations. (DS9 novels: Warpath, The Soul Key)