Nibelheim is Cloud's hometown, and was burned down in a fire caused by Sephiroth.
In Chapter 2, the group made it to Nibelheim, but only to see another battle waiting for them. In that old rubble-filled town, Alf's Brother, Chase, was waiting for him. And Alf became under the influence of Bokriseigel while in his hometown. Why? His old memories left an open door in his mind and Bokriseigel was able to get into his mind and control him. this caused problems with the group at first because they were confused as to why Alf was attacking his friends. Thanks to the help of Ashen, Linda, and fravir, They were able to help Alf find the strength to eliminate his influence.