To unlock the door in Burning Island Car that hold the Summon Daedalus and the extra boss(es) Ogre Titans, you first need to obtain the Sol Blade from the Apollo Sanctum and beat the game. Save the game after it prompts you to after you beat the game, then load the file. From Tonfon, sail all the way back to Burning Island Cave (volcanic island that has the counter clockwise swirling path to the top). Go to the bottom of the cave and go to the door which cannot be open before and the select it. After the text go into your inventory select the Sol Blade and use it.
|Burning Island Cave Door||Obtain Sol Blade and beat the game.|