Malladus

Malladus, the Demon King, is the antagonist of The Legend of Zelda: Spirit Tracks.

Biography
Prior to the events of the game, Malladus ruled over New Hyrule, and the inhabitants of the land lived in fear. Eventually, a rebellion broke out and the spirits of the land helped the inhabitants defeat Malladus. Despite this, nobody had enough power to kill the being, and the people could only muster enough strength and energy to subdue him with chains and shackles and bury him underground. The shackles, extending the land of New Hyrule in four different directions, became the Spirit Tracks, and the surrounding community used these tracks as transportation railways. During the game, Chancellor Cole separates Princess Zelda's spirit from her body and uses it in order to revive Malladus, as it is the only vessel suitable for him to inhabit and has the Sacred Power of the Spirits inside of it. In an attempt to stop him, Link and Zelda ascend the Tower of Spirits, which had been broken apart into segments, and secure the Rail Maps to restore the Spirit Tracks which imprison Malladus. However at the midway point in the game, Cole succeeds in reviving Malladus who then takes possession of Zelda's body, but finds adjusting to it to be quite difficult. Byrne, a servant of Cole, demands Malladus to give him the power he was promised for helping to set him free, but Malladus rejects Byrne. Immediately afterward, Cole and Malladus use the Demon Train to escape to the Dark Realm. In the hopes that Malladus doesn't adjust to Zelda's body immediately, Link and Zelda search for the Bow of Light as a means to force Malladus out of Zelda's body and the Compass of Light to find him in the Dark Realm (revealed to them by Byrne who had become good after his rejection by Malladus).

Upon finding the two artifacts, Link and Zelda enter the Dark Realm and find the Demon Train. After a short battle, Link and Zelda, in a Phantom Guardian's body confront Chancellor Cole and get past his defenses. Zelda then grabs Malladus allowing Link to shoot him with a Light Arrow. The Demon Train is destroyed and the contenders are returned to somewhere nearby the Tower of Spirits. Malladus is then forced out of Zelda's body and tries to reclaim it, but Zelda gets to it first with help from Byrne, who conjures a magical barrier. In vengeance, Malladus promptly destroys Byrne with a surge of dark magic. Malladus then consumes Chancellor Cole and possesses his body, transforming it into a giant beast. Due to the incompatibility of Cole's body, Malladus' hold on the vessel begins to slip. Determined to destroy the world, Malladus attempts one last destructive attack, but the crystal embedded in his forehead is stabbed by Link and Zelda with the Lokomo Sword, causing it to shatter. With the destruction of the crystal, light begins to shine from within Malladus' body, marking the permanent destruction of Malladus along with Chancellor Cole.

Etymology
Malladus' name is possibly based on a famous type of European steam engine: the Mallard. This seems probable due to the fact that many characters in Spirit Tracks are named in relation to trains. That particular train may have been chosen because it sounds like "malady". Furthermore, the European localiztion for Malladus' name is in fact "Mallard".