Any tips on defeating the boss

I've read several guides on TA for how to get achievements for completing the game and for getting no damage or killing no enemies. None of them seem to work any longer (the ritual they give takes me to a different room than what they say) and I can't get to the boss without taking damage, let alone kill the guy; I beat the first iteration and then go into the second room, but I can't seem to beat the boss and constantly get hit by him. Any tips?

Unfortunately, I don't have any tips, but I can let you know that the guides for the individual achievements were written when they were easier to unlock before Microsoft told the publisher that they couldn't alter the original requirements to the achievements once the base game had been released to the public.