The teleporter brings you back out to the encampment around the mine entrance, where you should be able to transform into a dragon. Even taking the main exit out, there should be plenty of room on that ledge to transform.
Did you try jumping off of a ledge and seeing if you could transform before you get too low into the poison? The outside edges of the encampment should provide enough room to transform, as would the open areas inside the walls.
Have you tried using the dragon stone to get back to the battle tower, and use the teleporter to go somewhere?
When you killed Ba'al did you get some loot, and a comment from Talana after grabbing it about how no dragon knight had ever defeated such a powerful demon in human form before?