Must Play:
Rules: Only zombie can go under barrier or you have to kill yourself.
Try to avoid the zombie while killing it with its reduced speed and high health.
Game Type:
http://www.bungie.net/Stats/Reach/FileSearch.aspx?fc=1&tags=SILVERBACK%20CHALLENGE&date=1
Map:
http://www.bungie.net/Stats/Reach/FileSearch.aspx?fc=4&tags=SILVERBACK%20CHALLENGE&date=1