Jalhalla (The Wind Waker)

This gigantic ghost rules over all poes. After reflecting light onto it with the Mirror Shield, you can lift it and throw it around. Jalhalla is a recurring boss in the Legend of Zelda series. Jalhalla is a colossal Poe and, seemingly, the leader of all Poes. Jalhalla is, in truth, only a mask, whose body is a conglomerate of several Poes.

The Legend of Zelda: The Wind Waker
Many years prior to the events of The Wind Waker, Ganondorf escaped the seal that had imprisoned him for a long time. He promptly attacked Hyrule again. However, unlike during his last conquest, the Hero of Time did not appear to thwart him, and Hyrule was left to the cruel will of Ganondorf. Despite meeting little to no challenge, Ganondorf feared that a future hero would rise up and challenge him. Ganondorf decided to prevent such a hero from utilizing the full potential of the Master Sword, should he ever obtain the feared Blade of Evil's Bane. To this end, he used the Triforce of Power and created two terrible monsters: the great sand worm Molgera, and the gigantic poe Jalhalla. Ganondorf sent Molgera to the Wind Temple to kill Fado, and Jalhalla to the Earth Temple to kill Laruto, the Sage of Earth. Jalhalla and some of Ganondorf's minions travelled to the Earth Temple. Leaving the minions behind to guard certain areas of the temple, Jalhalla explored the rest of the Earth Temple, looking for his victim. He found Laruto in the temple's chamber, where she was was praying to the gods to lend their power to the Master Sword. The gigantic Poe attacked and killed Laruto, stealing her soul and rendering the Master Sword completely powerless, as Fado had already been killed by Molgera prior to the slaying of Laruto.

Several years later, Link, the Hero of Winds, as Ganondorf foresaw, obtains the Master Sword, only to find it near useless against battling Ganondorf. He travels into the Earth Temple, where he is contacted by the spirit of Laruto. The former Sage of Earth asks Link to find a successor and pass on the knowledge of the Earth Sages. In order to help him pinpoint the successor, Laruto teaches Link the "Earth God's Lyric". This descendant turns out to be Medli, whom Link brings to the temple. Laruto tells Medli about her true purpose. Together, Link and Medli brave the many trials of the Earth Temple and eventually finds the room filled with many poes is. Upon seeing Link, the Poes jump into a large mask, forming Jalhalla in the process. Link uses the Mirror Shield found in the Earth Temple to destroy Jalhalla.

Despite his defeat, Jalhalla appears again in Ganon's Tower. The battle is fought in black and white; symbolizing that the battle is a "flashback" for Link.

Battle
To defeat him, Link must use the Mirror Shield to shine light on him, rendering him corporeal. Link must then pick him up, using the power of the Power Bracelets and fling him into one of the spiked pillars around the room, which causes him to explode into a group of Poes, allowing Link to pick them off one by one. When all the Poes are destroyed, Jalhalla is defeated, but his mask attempts to escape. Light hits his mask, which paralyzes him and causes him to fall to the ground and shatter. It is possible to collect the iron boots previous to this battle making his wind attack far less effective.

During the second battle, the mask is restored faster than usual when he explodes into Poes.

Video
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The Legend of Zelda: Four Swords Adventures
Jalhalla appears as a boss. The four players must actually enter the ghost, attacking his sensitive and vulnerable core, which itself has the appearance as a meek ghost.

Etymology
It is likely that Jalhalla was named after Valhalla, the Viking's version of Heaven, although his name also sounds similar to Jahannam, the name of the Islamic equivalent of Hell.

Trivia

 * Battling him in Wind Waker is similar to fighting Boolossus in Luigi's Mansion. Except that Boolossus shrinks after defeating a few boos.