Emperor Zeba is the ruler of the Underground Empire Tube and the primary antagonist of Hikari Sentai Maskman. He is a mysterious figure who usurped control of Tube after killing off its original rulers, the Igam family. He desires to conquer the surface world and spread darkness all across it.
He was voiced by the late Seizō Katō, who also played several other Tokusatsu villains, most notably Dai Satan in Kyoryu Sentai Zyuranger, General Jark in Kamen Rider Black RX and Alien Mefilas in Ultraman and Ultraman Mebius.
Zeba was originally Lethal Doggler II, the son of the original Lethal Doggler, a beast that terrorized the underground until being slain by the Igam family. Desiring revenge, Lethal Doggler II devoured its parent to gain more power. Disguising himself and renaming himself Zeba, the tyrant overthrew the Igam family and took control of the Tube Empire.
Killing every member of the Igam family except for their twin daughters, Igam and Iyal, Zeba soon learned that the two daughters would be his downfall and thus kept them apart for most of their lives.
Hikari Sentai Maskman
Desiring to add the surface world to his dominion, Zeba sent Iyal to the surface as a spy to scout it for invasion, though this backfired when Iyal fell in love with Takeru and warned him of the Tube invasion. As punishment, Zeba sealed Iyal within ice.
At the end of the series, Zeba raised the Underground Castle to the surface, intending to use it to spread darkness across the surface world. Traveling to the surface, Zeba battles the Maskman, initially having the advantage due to fighting them in his own Dark Aura domain. However, Iyal and Igam combine their powers with the Igam Royal Pendant and combine that with the five combined Auras of the Maskman to expose Zeba's true form as Lethal Doggler II. Lethal Doggler II is then blasted by the Jet Cannon, but survives and enlarges himself. Battling Galaxy Robo, Lethal Doggler II is finally finished off by the mecha, ending his cruel reign over the underground.