Husband has cirrosis caused by hepc but there is another unidentifiable factor attacking his liver, what else could be attacking his liver, not hiv?

Viral hepatitis. Likely not HIV itself but some of the anti-hiv meds can cause liver disease as can a number of other meds. Other viruses such as hepatitis b can coinfect. Ethanol can also be a factor.
Alcohol?? The most common combination that accelerates the damage of either hepatitis c or b is alcohol. He should not be drinking anything alcoholic. A competent hepatologist (liver specialist) will do all the tests to rule out autoimmune hepatitis, primary biliary cirrhosis, wilson's disease and other obscure causes of liver disease. Make sure his GI specialist is, in fact, a trained hepatologist.