First off, you have to kill the three guards first to get them out of the way. They are pretty easy so it shouldn't be too hard. It might be best to start the battle with a quickening. Try to get in AT LEAST 3 hits in the quickening chain so that you can get the Inferno area attack. The more hits you get in the stronger Inferno will get. Once they are finished, then focus your attack on Judge Ghis. It might also be a wise decision to have cure or potion gambits sitting at the top spot. It might also be a good idea to have at least one ranged fighter. For example, equip a gun or bow to one of your characters so that they can sit back and not worry about taking damage too much. If you have the best armor equipped then it should help out. Also, equip a shield to one of your close-ranged fighters. As Judge Ghis's HP starts to fall, his attacks become faster and more powerful. With enough patience you can win the battle. Good luck.