Board Thread:General Discussion/@comment-6008001-20130203234601/@comment-1837917-20130204001436

Find yourself a damn good fire weapon, cook up some Psychoserums, bring a load of Paintballs, aim for the head, dodge his attacks and keep attacking until you break the horn, thus cancelling his invisibility. Pretty vague answer, I know, but if you need any more help check out the guides forum. That's what it's there for~