i killed yagluth using the fenris armor for the speed bonus as well as the fire resistance u get from it. and i used frostner mainly but when i got low enough i ran away and fired frost arrows and kept my distance . good tip.... clear the area around the boss area for goblins and loxes and bugs. i died two times but since i had a portal closeby it was easy to get back and get my things. use the stone pillars to hide from the fire laser and the meteors.