Octomus the Master

Octomus the Master (better known as The Master) is the leader of the forces of darkness, the supreme ruler of the Underworld, and the main antagonist of Power Rangers Mystic Force.

First Defeat
Octomus was the lord of the dark forces of the Underworld, greatly revered by the denizens of his realm to the point that they called him only "The Master". When the forces of the Underworld attacked the surface world, the Ancient Mystics battled them in what was known as the Great War. Eventually Octomus' forces were driven back into the gates of the Underworld, which were sealed shut by the Gatekeeper, Niella. The warrior, Leanbow, was sealed in as well and he imprisoned the Master in his Pit, but not before Octomus used his dark powers to transform Leanbow into Koragg the Knight Wolf, his loyal servant.

Rise of the Underworld
However 2 decades later, the forces of the Underworld began their return and Octomus kept in contact with them from the Pit via a white pool that would turn red to announce his presence. The Master often had to deal with arguments amongst his forces, usually involving Koragg due to his preference for honorable methods. At one point, Imperious put Koragg on trial for being a failure to the cause, but Octomus chose to rule in favor of the Knight Wolf. Later Imperious attempted to bring about the Master's return after the failure of his attempt to overthrow him. His plan was to use the Mystic Force Rangers' Legend powers to give Octomus the strength to rise and it succeeded until Udonna attempted to interfere, only to be almost killed by the Master. Koragg interfered and became Leanbow again, however Octomus was about to almost rise to the surface. Leanbow headed back into the Underworld so as to fight and seal away the Master again and succeeded, stopping and seemingly destroying him.

Return
However the Ten Terrors sought to bring back Octomus by attacking the surface world, while following the Rules of Darkness. But as time went by and their attempts seemed to have no effect, Sculpin began looking for answers. He went to the Lake of Lament and asked it to show him the Master, only to be greeted by an image of Leanbow, changed into Koragg's body but still possessing his free will. He told the Terror that Octomus would never return as long as he was still around and Sculpin began seeking a means of finding him. Sculpin finally succeeded in finding him and took the Master's spirit from him, giving it to Gekkor to keep safe. Later Matoombo was selected as Octomus' host body and though the Terror tried to avoid this fate, the Master could not be denied and his spirit forcibly entered Matoombo's body with his form bursting forth. The Master proceeded to possess Nick Russel, the Red Mystic Ranger, and turned him a version of Koragg, one far more destructive and malicious. He proceeded to attack parts of the forest and while the rangers were kept busy trying to free him, Octomus attacked the Mystic Realm and seemingly destroyed the Mystic Mother, matriarch of good magic. Leanbow and Daggeron went to confront him, only for the Master to devour their Knight powers, before finishing them off. Octomus then went to Briarwood to battle the rangers himself and showed them a vision of an Earth he had ravaged. He then devastated their Manticore Megazord, swallowed part of their magic, and forced them to run, though Nick managed to wound the Master and get the rangers back to the real world, but at the cost of all their magic. However, Octomus' victory was prevented after Itassis and Necrolai turned on him, resurrecting Leanbow and Daggeron, the Mystic Mother turned out to be alive, and the people of Briarwood and the forest united against him. They managed to restore the rangers' magic, who used Octomus' ability to devour magic against him by giving him too much and causing him to overload and explode.

Powers and Abilities
Octomus is the most powerful dark magic being in the universe and is able to devour magic from other beings, but there is a limit to how much he can take in, before it proves too much and destroys him. The Master also seems able to use parts of himself to create weapons for his minions, since one of his eyes was in Koragg's shield, one of his fang's was used for Morticon's sword, and some of Octomus' claws may have been used for magical items in Necrolai' possession called the "Claws of the Master".

Trivia

 * Octomus is never actually referred to by that name in the series and is always called "the Master". However one of the episode descriptions in the iTunes Video Store called him Octomus.
 * His counterpart in Mahou Sentai Magiranger, the Super Sentai series that Mystic Force was adapted from, was N Ma.
 * Octomus' form is reminiscent of the Lovecraftian creature, Cthulhu.
 * Despite only appearing for a few episodes, Octomus is definitely one of the more serious and darker Power Rangers Villains.
 * Octomus' quote about the ranger's true purpose has been considered one of the darkest quotes from the Power Rangers Franchise ever.