Voiced By: John Leigh
Ruler of the Underworld, Octomus for most of the series sent his minions to take over the surface world for him. Octomus nearly succeeded in leaving the depths of the Underworld after he stole the rangers Legend Warrior powers but was stopped by Leanbow and trapped within him until the Ten Terrors steal his soul back. He chooses Matoombo as his host and begins his conquest of the surface world. He first goes after the Mystic Mother and kills Daggeron and Leanbow. He nearly succeeds in killing the Mystic Force Rangers if it weren’t for Itassis taking him out of commission temporarily. He grows however but is taking down by the Mystic Force Rangers feeding him an endless supply of magic.
Voiced By: Andrew Robertt
General of the Underworld, Morticon lead the armies of the Underworld from the inside due to him being unable to leave the underworld. He does leave the pit temporarily after Koragg steal the rangers megazord power but is quickly sent back there. He does succeed in leaving the pit a second time after the gates of the underworld rise to the surface world. He is destroyed though by the Titan Megazords Mystic Strike.
Voiced By: Donogh Rees
Queen Of The Vampires, Necrolai serves whoever is leading the armies of the underworld. She has a daughter named Leelee who eventually left the underworld to live as normal human. After Itassis is destroyed by Black Lance and Sculpin, she decides to go rogue and resurrects Itassis and save Udonna from Sculpin. After reviving Daggeron and Leanbow, Necrolai is purified and turned human.
Voiced By: Geoff Dolan
Koragg came to be after Leanbow was trapped in the underworld and transformed into a servant of Octomus. Koragg is shown to be well skilled in both the art of magic and fighting. He is also shown to have an honorable code as he won’t destroy an opponent unless he or she is of equal strength. Koragg eventually learns of his true identity of Leanbow and defects to the side of good.
Voiced By: Stuart Devine
Imperious was once a Mystic named Calindor who defected to the side of evil during the Great Battle. He was trapped in a cave for many years up until Necrolai found him and brought him to Octomus to be reborn as Imperious. There he replaced Morticon as the leader of the Underworld and unlike Morticon decided to use his plans that required intelligence over brawn. He summoned the Barbarian Beast to set out on a plan to capture the genie Jenji and for a short time the planet was ruled by the Morlocks. Imperious was shown to be very power hungry as he desired to rule the Underworld and plotted to get rid of Octomus for a short time. After learning that he could never get away with it, he decided to gain his masters favor by stealing the rangers Legend Warrior powers so that Octomus may get stronger. Prior to Octomus rising out of the Underworld, he challenged his old rival Daggeron to a duel, which he lost and inevitably turned to dust.
Voiced By: Greg Smith
Magma was the first Terror chosen to attack the surface world. He gave the Mystic Rangers a real challenge up until Maddie stopped him with her Water Power. He grew but was destroyed by Sculpin after it was revealed that he lost the game he created.
Voiced By: Andrew Laing
Oculous was the second Terror chosen to attack the surface world. One by one, Oculous hunted the rangers until there was one left standing. Oculous is taken down by Nick’s newly acquired Battlizer.
Voiced By: Sally Stockwell
Serpentina knew early on that she was going to be chosen to attack the surface world so she sent Hekatoid to take care of the rangers prior to being chosen. He does succeed in preventing two of them from morphing which aides her in eating the rest of them. After Nick and Vida gain their magic back, she is taken out by Nick’s Battlizer. She grows and is destroyed by the Manticore Megazord.
Voiced By: Dalas Barnett
Megahorn impatiently waited to be chosen by the Stone Of Judgement to attack the surface world. When chosen, he attacked the city in his more dragon-like form until the Snow Prince transports him to his dimension. He breaks free however and is challenged by Daggeron to battle one and one and is defeated. He grows and gets some help from Black Lance and gives the rangers a hard time up until Leanbow gets Black Lance out of the fight. He is destroyed by the Solar Streak Megazord.
Voiced By: Charlie McDermott
Hekatoid succeeded in capturing Udonna prior to being chosen by the Stone Of Judgement. After being chosen, Hekatoid planned on releasing his poison frogs on the Earth but was stopped by Daggeron using his Solar Streak for a short time. After the rangers played a few of his games, Hekatoid succeeded in capturing the rangers powers up until Udonna came in to aide the rangers with her reacquired ranger powers. Hekatoid is taken down by the combined efforts of the Mystic Rangers and the White Mystic Ranger.
Voiced By: Cameron Rhodes
Matoombo was chosen as the vessel for Octomus to be resurrected in. Prior to being chosen by Octomus, he befriends Vida and defects to the side of good. He decides to go the Lake Of Lament so that he may sleep there for eternity so that Octomus may never rise up. However, he is stopped by Sculpin and Octomus destroys him and reconstructs his body to match his own image. He is revived however after Octomus is destroyed through unknown circumstance.
Voiced By: Mark Ferguson
Gekkor was sent by Sculpin to prevent Matoombo from reaching the Lake Of Lament. He is stopped however by Leanbow and is destroyed by him.
Voiced By: Josephine Davidson
Itassis is given the task making sure that the rules of darkness aren’t being broken by her cohorts. Unlike most Terrors, Itassis craves knowledge over powers and after learning that courage is the one thing that the rangers have that the force of the underworld do not, she defects from her allies and is destroys for it. However, she is revived by Necrolai and is last seen being taught by Daggeron about courage.
Voiced By: Derek Judge
Black Lance is shown to be Sculpin’s second-in-command and aides Sculpin in whatever he asks, even if it includes breaking the rules of darkness. He is given the task of destroying the rangers after Udonna is captured by Sculpin but is destroyed himself by the Mystic Rangers.
Voiced By: Peter Daube
Leader of the Ten Terrors, Sculpin’s main goal is to make sure the Ten Terrors are following the rules of darkness so that Octomus may return. His first goal of resurrecting Octomus was to find Leanbow and reacquire Octomus soul from him. During the final battle, Sculpin succeeds in capturing Udonna but is stopped by a revived Itassis and is destroyed by her.
The Hidiacs serve as footsoldiers to the Morlocks.
Stronger than regular Hidiacs, the Styxoids are usually shown leading the Hidiacs in battle.