The Once and Final King
Defeat the Shade inside you within three and a half minutes.

This is the final battle of the game if you're going for Ending A or B. Skip all cutscenes, don't worry if you miss the trophy in your first playthrough, it will be much easier in New Game+

Hit the boss with Dark Hand, or Dark Lance if not in range. He'll jump out from under the ground at time, so always be on your guard. Once his health reaches half he'll start flying, hit him with several Dark Lance's.

For his final attack, he will be at the back of the room and unleash a barrage of magic, evade and hit him with your sword. Afterwards, you'll be teleported to the other end of the room, repeat the process two more times. Please note, you will be unable to use magic for the final stage of the battle. A cutscene will play and the trophy will unlock.