- “The body dies... but the spirit lives on.”
- —Zemus, shortly before turning into Zeromus
Zemus (ゼムス, Zemusu?) is the main antagonist of Final Fantasy IV. He is a Lunarian who wants his brethren to come out of their long slumber and populate the Earth. He has formidable mind-control powers that he uses to manipulate various characters, especially those with Lunarian blood.
Zemus appears to have been the only voice among the Lunarians advocating world domination. The rest of the Lunarians wanted to wait for the people of Earth to evolve to the point where the two races could coexist. Zemus was forced to sleep, and the moon's crystals sealed him within the moon, but because of his immense psychic powers, his mind remained awake and searched for ways to accomplish his plan. He manipulated Kluya's son, Golbez, and used him to achieve his goals.
Zemus manipulates Golbez into summoning the Giant of Babil, a massive android capable of eliminating life from the planet to make way for the Lunarians. When all of the crystals were gathered and the Giant roams the Earth, Fusoya, Cecil, and his allies infiltrate the Giant and destroy its central processing unit and Fusoya breaks Zemus's mind control over Golbez. Furious at being made to commit atrocities, Golbez swears to kill Zemus and leaves with Fusoya for the moon's core.
In the ensuing battle, Zemus resists Golbez's and Fusoya's spells and taunts them into killing him by simultaneously casting Meteor. Despite Zemus's death, his hatred lives on as Zeromus. Cecil and his allies, with the help of the prayers of their supporters on Earth, vanquish Zeromus, ending his threat for good.
Zemus's main power is his ability to control the minds of others remotely, particularly Golbez and Kain Highwind (indirectly). Strong feelings can interrupt this power for a time, as seen when Kain is stopped by Rosa from killing Cecil. Additionally, Fusoya is able to break Zemus's control over Golbez and make him remember his true identity.
- Main article: Zemus (Boss)
Zemus is a cut-scene battle where Fusoya and Golbez join forces to fight it. The battle is purely cinematic.
Zemus appears as a card in the Final Fantasy Trading Card Game.
Zemus is the Amharic word for "Prayer".
- One piece of unused dialogue exists, "You are entering into my realm, the Zemus-Zone. No one can ever escape from my minions! Perish in the Darkness before you reach me." A speech given by Zemus, taunting the party telepathically. This was probably intended to be displayed upon entering the Lunar Subterrane or the Lunar Core. The "Zemus-Zone" is also an unused location name.
- The party being defeated by the final boss and then revived by their allies alludes to a similar scene in Final Fantasy III.