Throughout the dungeon are Bluebane Mushrooms, for What Does Not Kill You.... You must break them before you kill Corpsemaw or the quest will not update.
Cross the bridge and clear to activate the first stone. There are spiders and ghouls here. Also, the glade is ringed with blue mushrooms needed for several quests. Back across the bridge and right to more ghouls and kobold archers. Mushrooms and an airship part are beside the path. Activate 2 stones to open the door.
Three stones are spread around the woods, as are blue mushrooms and airship parts. Watch for red dots on your minimap to help guide you to the stones. Bats will be active at each stone but as you approach the stone undead will rise: skeleton warriors and ghouls. You may also see kobold archers and a troll.
In the north-east corner of the forest is a small glade with ghouls, spiders and kobolds... and an airship part and 2 wood treasure chests!
He also has some ghouls and spiders. From time to time he will stand up, raise his fists over his hed then strick the ground, sending out a line of grave cold in front of him. If you get caught, pound the A and D keys, alternately, to break the ice.