Demise

"Extraordinary. You stand as a paragon of your kind, human. You fight like no human or demon I have ever known. Though this is not the end. My hate... never perishes. It is born anew in a cycle with no end! I will rise again. Those like you... Those who share the blood of the goddess and the spirit of the hero... They are eternally bound to this curse. An incarnation of my hatred shall ever follow your kind, dooming them to wander a blood-soaked sea of darkness for all time!"

- The curse of Demise

Demise is the main antagonist and final boss of the Skyward Sword. Long ago he and his horde of demons and creatures broke through a fissure in the earth and sought out the Triforce. However, he was defeated and sealed away by the goddess Hylia.

Throughout the events of the game, Demise attempts to break free of his seal in the form of The Imprisoned, but he is consistently repelled through the efforts of Link and Groose. At last, when Link obtains the Triforce, he manages to defeat Demise permanently. However, Ghirahim kidnaps Zelda and takes her to the past through the Gate of Time, where he begins a ritual to revive his master. While Link manages to defeat Ghirahim, he is too late to stop the resurrection of Demise. Demise begins to absorb the soul of Zelda to gain unstoppable power, but he is impressed by Link's willpower and invites him to do battle. To Demise's shock, Link manages to defeat him, but in his dying throes, he places a curse on Link and Zelda. For all eternity, they and their descendants shall be pursued by a manifestation of Demise's hatred. With that, Demise is sealed away within the Master Sword, where his remains begin to decay.

Trivia

 * The sword he holds is a dark version of the Master Sword. It was pulled from Ghirahim's chest, and appears to contain the remains of his soul.