Cyanogen was a gas that was poisonous to nearly all those who breathed it. However, a few species needed it for survival, in particular the Celegians. Trandoshans were immune. It was an important factor in the defeat of Naga Sadow's Massassi forces on Kirrek during the Great Hyperspace War. The Celegian Jedi Master Ooroo sacrificed himself by tipping his chamber filled with cyanogen into the Massassi, and, as it shattered, it killed many warriors. He was subsequently poisoned by oxygen. Cyanogen was also used on Meetra Surik in the Jekk'Jekk Tarr Cantina, but it failed to subdue her.