O yeah, I've listen & looked at the video that's just coming on the Newspage of LS side today ...
always find it very handy and good there is no "anti-dragon-zone" at the Dragon Cliff Castle ... but never thought deeper about it : to change into a dragon during that, indeed, very hard battle !!
So first killing Markthum ...and then, yes then ...

... I really wish to try that next time !