Demise

Demise, the demon king, also known as The Imprisoned, is the final antagonist of Legend of Zelda: Skyward Sword, and is the one behind the central antagonist, Ghirahim.

Long ago, Demise appeared from within the earth and invaded the land, killing many without mercy, before the goddess, Hylia, sealed Demise away. A Seal Spike marked his seal in the Sealed Grounds, at the bottom of a great pit.

At some point, Demise transformed his sword into a demon named Ghirahim, who, once the seal began weakening, began to set about reviving Demise from his imprisonment using the soul of Zelda, Hylia's reincarnation. After Impa escaped with Zelda into the past, and a Gate of Time was revealed in the Sealed Grounds, the seal on Demise broke and he escaped, however, Link defeated him, driving the Seal Spike into his skull and resealing him below the Sealed Grounds.

Demise later escaped again, but was again defeated and sealed up by Link, with help from Groose. This happened a third time as well. As Demise was about to escape a fourth time, Link made a wish with the Triforce, causing the Statue of the Goddess to fall and crush Demise, obliterating him.

However, Ghirahim traveled to the past with Zelda and, by means of a ritual, gave her soul to Demise, who was able to return to power. After transforming Ghirahim back into a sword, Demise told Link that if he wished to fight him, he should enter his own dimension away from any distractions, otherwise, he could just wait for Demise to destroy the entire world. Link entered the dimension and fought Demise. Eventually, Link defeated Demise by stabbing him with a Killing Blow using the Master Sword. Before disintegrating into black smoke, Demise said that his hatred would be reincarnated to torment Link and Zelda's descendants. What remained of Demise's consciousness was absorbed into the Master Sword, to decay over time until there was nothing left.

Trivia

 * Demise shares the same voice actor as Ganondorf. His final form looks similar in appearance and size to Ganon. The way he is defeated is similar to Ganondorf's defeat on Twilight Princess.
 * The word "demise" is a synonym for "death".
 * It is unknown if Demise has any connection to the demon king, Malladus, in Spirit Tracks.