Once again, you need to approach him but this time, Edward will not be gentle. Go forward and to the right. Repeat this to get closer to the temple. When you get to the right-hand side of the temple, go around to the back of the temple. Go to the right-hand portion of the temple, behind the off-shoot section. user that to start the climb up the temple. Make your way to the Viewpoint above Vane. From there you can easily get Vane with an Air Assassination.