Kristoff.9574

I also thought this was impossible. But then I realized that there is a skyscale mount you can borrow in The Overlook. You have to go in the opposite direction of the time-trial thing. Then you have to land over and over again to restore your energy so that you can fly upward again. But eventually, you can make it to Blood Keep and fly up to the top where the vista is. So yeah, it is possible even if you don't have a skyscale mount of your own. You can just borrow one.