Direct answer
Objectives follow journal display order. Some depend on your choices; follow the active objective in the game.
Result
Geralt knew he could only defeat Eredin with the help of mages and on his own terms. Since the King of the Wild Hunt was traveling on the Naglfar, the spectral vessel known from Skellige legend, somewhere between worlds, our heroes had to summon him back and somehow cut off his escape route. Such a feat could only be performed by a group of mages acting in concert and aided by a legendary elven artifact - the Sunstone.
