Domestic abuse is as much mental and emotional abuse as it can be physical. Even without narcissism an abuser is very good at making their victim believe the abuse is all their fault, that there is something wrong with them, that everything will be perfect if only the victim can do and be what the abuser wants. Many will be too scared to leave because their abuser has convinced them they are so useless and helpless that they won't be able to survive in the real world without the abuser. They break their victim down over time. Some victims will even come to believe that not only is the abuse their fault, but that it's exactly what they deserve. And eventually for many victims, the abuse becomes so normalized, especially if it isn't physical, that they lose sight of reality, they don't realize just how abusive and wrong and abnormal their situation is.