Successfully complete the game to unlock the Hardcore difficulty.
Get a 100% game completion to view an extra animation sequence.
Successfully complete the game to unlock the "Staff Credits" option at the "Extras" menu.
Although the Daemon Lord Reborn is normally defeated by depleting its health and triggering a finishing sequence while it is stunned, there is a glitch that allows the Boss to be stunned at the beginning of the fight. To do this, wait until the Daemon Lord attacks, and use the magnetic railing above to get to the opposite side it is facing. Make sure to give yourself enough distance from the Boss so it will not counterattack with its tail. Drop down, charge up the bat projectile, and time its release so that it collides with the Daemon Lord's sides as it turns around. If done correctly, the Daemon Lord will now be stunned, and open for a finisher -- which normally is not possible until several phases of the fight have passed. Although the following sequence will appear strange due to Alucard and the Daemon Lord clipping though objects that normally would not be there, the cutscene will nonetheless conclude with the Boss being defeated, and you being awarded the Demonic Wings.