Beat Rapthorne.Use The Bird Sole Stone. Thers a Place Some where Near Argonia.

use the sole bird stone and fly Argonia and there should be like this boat thing and when
you land you should see the portal

You must fly near Baccarat. When you see a small wooden stand and you are flying over it
press triangle to land and answer yes.

once you have beaten rhapthorne once,use the soulstone,hover above chateu felix. follow
the path to argoia. you will see a rather boat looking thing on a mountain. land on it.
walk up to the big stone the dragon statue is on top of and press X.thats it