Killing some Kobolds

I am trying to get into my home town. this is complicated by the fact that the surrounding area and the town itself is flooded. I do the only thing I can, and sneak in through the sewers, which are still completely dry, and just like the sewers in Dungeons and Dragons Online(complete with quests.) Unfortunately the sewer is full of kobolds, fortunately I am now Artemis Entreri. I kill my way through the kobolds, but I come across a sealed door. I open the door and inside is this giant floating flaming head. I try to kill it but can't do anything to it. I apparently multiclassed into cleric, because I cast some buff spells on myself. I still can't harm the monster and run. I make it to the city, kobolds nipping at my heels. I run out of hit-points as I climb out of the sewer, but I luckily have the Die Hard feat, and am still able to run. I make it to the beach (created by flooding) and find a cleric there willing to resurrect me when I died.