Demise is the main antagonist/final boss in The Legend of Zelda: Skyward Sword. In the game, long ago, he broke through a fissure in the earth, but was sealed away by Hylia.
When Link enter a portal to the battleground, Demise is facing away from Link. He congratulates Link for his courage, but says Link will fall. At the begging of the battle, Link may not use the Skyward Strike. On the second phase, the stage will fill with lightning. If one of these bolts hit Link's sword when he is holding it up, the strike will charge, causing Link to be able to attack.