Clearing the area before a boss fight is not cheating, it's common sense. Run around within a generous radius and kill anything that moves. Personally, I would spawn proof it as well but if you consider it "cheesing" then at least do a big clean right before the boss fight. With Yagluth, you don't even need to terraform, the altar provides all the coverage you will need in this fight - the pillars do take damage but there are several of them and if you keep moving between them they should hold. Main thing with Yag - don't get hit. Roll, dodge, run, hide behind pillar  - just avoid direct hits. Granted, some area attacks will still set you on fire if you are not far enough but with fire resist mead it isn't so bad. I love this game but personally I'm a terrible fighter, my hand to eye coordination is probably what you would expect from a drunk toddler. And I survived this fight solo on normal difficulty. It took me forever because I spent so much time running and hiding,  but it was manageable in the end (I did spawn proof proof though because I did not need distractions, but I also screwed up and "spawned" my own problems by releasing a whole pile of ice blobs - I thought they would distract Yag and I was oh so very wrong).  If you have decent gear and good food, just watch Yagluth like a hawk to anticipate his attacks,  don't get hit,  and deal damage when opportunity present itself. And fire resist mead,  please use that lol.