What can I do in my current job situation.?

I have a boss who is very abusive. He bullies, insults, lies, changes direction, blames others, and verbally assaults the employees self esteem every day. I have seen other employees quit because of this, and others have complained to HR but nothing has been done and now they're the victims of retaliation by the boss. He has even said out loud that he would kill anyone that would cost him his job, so I am also physically scared of this person. I realize I have the option to find another job but I like this job and I have been offered a promotion but would still have to work under the same boss. Quitting would be my last resort but I cannot function under the stressful working conditions, my work is beginning to suffer. What options do I have?