First battle of Ossus

The planet Ossus is the third planet in the Adega system. It's history is tied to the history of the Jedi and Sith wars and it is even speculated that the Jedi Order originated there. During the Clone Wars, it was home to large cities and a Jedi stronghold. Enemies of the Jedi such as the Confederacy would find this to be a prime target.

At this point we don't know exactly what happened. However, right before the Second Battle of Rhen Var, Mace Windu stated that, "Ossus will fall within days." Apparently, the Confederacy took the planet early in the war. Whether any attempt will be made to take it back is unknown.

Jedi Master Ood Bnar managed to survive all of the fighting on Ossus. This was because, in an attempt to preserve a cache of lightsabers, Master Ood Bnar initiated his lifecycle change, becoming a gnarled old tree with the lightsabers entangled in his roots. No one would suspect a tree of being a Jedi and therefore he survived the Clone Wars.