I am in a swamp I don't know, do you get to the third temple key.....

I think you talking about Dark auther in the Torvus Bog were you need to get the third temple key. At the entrance of venomous pond (were you have just entered trough the Brooding Ground), roll into a morph ball, look around and you should see a small tunnel, roll trough that, get up into combat mode and look for a graplling hook, grapple onto that, swing across and now you have just recived your third temple key,

If however you already got a key from there, then first you need to go into light Auther, get into the hydrodanamo Shaft, get to the bottom,and before you take a turn to get to the door into the hydrodanmo Chamber, u will see a ledge or a hallway at the top whatever you like to call it, jump up there and enter the portal, and right infront of you is the temple key,