Lunar Subterrane The Lunar Subterrane , also called Lunar Core , is the final dungeon in " Final Fantasy IV " . It ' s a massive cave complex , filled with strong monsters . It can only be accessed from Crystal Palace once the Giant of Babil has been destroyed . The caverns contain a great deal of hidden passages and strong monsters , including dragons . Crystal equipment , the game ' s strongest , exist here for Cecil in the SNES and PlayStation versions . There are also many monsters hidden in treasure chests , and at the bottom of the cavern lay several sealed relics guarded by minions of Zemus . Eventually , the caverns lead to an area where the floor consists mainly of shiny tiles . The walls are still made of rock . This area is titled the Lunar Core in the game ' s " Advance " version , but is part of the Lunar Subterrane in all other versions . In the Easy Type version that was only released in Japan , there ' s a save point on one of the last floors in the subterrane . In reference to this , " " brings it back , but has replaced it with a healing tile . The area is infested with semi - boss monsters as Random encounter s , such as Behemoths and Red Dragons . Lower levels also contain Zemus ' s Malice , Zemus ' s Breath , and Deathmasks , enemies unique to this area . The boss Ogopogo also lurks here guarding the strongest weapon for Edge . The upper areas of the core are connected via stairways , but lower areas are connected via teleporters . In the deepest area , the party can find Zemus . Beyond this lie the deepest areas of the core where the Lunarian s are sleeping . Story . " Final Fantasy IV " . Cecil and his friends descend the Lunar Subterrane after destroying the Giant of Babil , following Fusoya and Golbez , who head for the core in order to defeat Zemus . After going through several battles in the subterrane , the heroes finally meet Zemus , Golbez , and Fusoya , who are battling . Golbez and Fusoya are able to defeat the evil Lunarian , but his hatred is revived as Zeromus , who easily knocks the party unconscious and defeats Golbez and Fusoya . With the help of the prayers of his friends , Cecil gets back on foot and uses the Crystal Golbez gave him , which in turn gives Zeromus a physical body , allowing him to be defeated . With Zeromus ' s death , Golbez and Fusoya head to the sleeping room deep within the Moon , while Cecil and his friends return to their planet . " " . The Lunar Subterrane reappears in the Lunarian ' s Tale in " The After Years " . Golbez awakens in the Chamber of Sleep , sensing something wrong with the Crystals , and goes through the subterrane to the surface , meeting with Fusoya along the way . After investigating the Crystals and the Impact Crater of a meteor , the two defeat a Mysterious Girl they find there . Returning to the Crystal Palace the girl seems to return , and summons Leviathan . The two defeat her again , and pray for the Lunar Whale to come to them from the Blue Planet . Suddenly , one of the Crystals shatters , and a new girl appears and tells them she does not need them . Fearing for the other Lunarians , Golbez and Fusoya race back to the Chamber of Sleep , but before they reach it , all the Crystals shatter , reviving Zeromus as Zeromus ' s Malice . In the ensuing battle , Zeromus Malice uses Big Bang and Fusoya teleports Golbez away to the Lunar Whale . Locations . B3 . A pedestal that holds Murasame is found in a corner of B3 . Like all other corners and rooms that lead to weapons in this dungeon , it is not accessible by the main path , but by going through a series of detours or secret passages . This pedestal is found by the west secret passage from the dungeon ' s entrance ( B1 ) , then taking the teleporter that leads to B2 . The player should head west to find another teleporter that will take him to B3 . The pedestal is found in the far - left corner of the room . Murasame is guarded by a White Dragon , which must be defeated to obtain the katana . The room in B5 where a Red Fang is found is the only room in the whole game where the extremely rare Flan Princesses can be fought — running into them as random encounters is nearly impossible . By using a Siren , they will attack in pairs of three . The pedestal that holds Ragnarok , Cecil ' s ultimate weapon , is found in B5 , but is accessible from B6 . To reach the specific room , the player must go down the set of stairs in B6 , then go through the secret passage to the west ( hard to spot at first because the character floats , as there ' s no ground ) . From here , there is a secret passage into the wall , to the east , then down the set of stairs , which completes B6 ' s map . Heading south then east will lead to a teleporter which will warp the player back to B5 . The South exit leads out of the room , and by heading east , Ragnarok ' s pedestal is found . It is guarded by Dark Bahamut . B7 . Two of the B7 ' s three inner rooms hold optional boss encounters guarding two relics and an ultimate weapon . It is also the last room of the Subterrane — the last room of this floor is the exit that leads to B8 , the first room of the Lunar Core . The pedestal is the second room in the map , the one after the room with the dungeon ' s second save point . The Holy Lance , Kain ' s ultimate weapon , is guarded by a Plague Horror , and must be defeated to obtain the lance . The next room from the previous one holds two treasure chests , which contain one Ribbon each . If the player goes for them , a Lunasaur will attack them , and it must be defeated to obtain the two relics . After defeating the Lunasaur , the player will be free to open the two treasure chests . The pedestal holding Masamune , the last of Edge ' s ultimate weapons , is found in B8 . If the player doesn ' t bother filling out the map , it will be easily missed — it is found on the south - east corner of the map . Masamune is guarded by Ogopogo , a dark Leviathan . To obtain the katana , it must be defeated . It is the second - to - the - last floor of the dungeon . If the player has filled out all dungeon maps in the entire game , the Treasure Hunter augment will be obtained as soon as this floor ' s map is completely filled out . B12 is the last floor of the dungeon , and where the party fights Zeromus . Musical themes . The background music that plays inside the subterranean areas ( B1 - B7 ) is " The Red Wings " . The background music that plays inside the moon ' s core ( B8 - B12 ) is called " Giant ' s Dungeon " , the same as the Giant of Babil ' s . Other appearances . " Dissidia Final Fantasy " . The Lunar Subterrane is the representative arena of " Final Fantasy IV " . Firion battles Jecht here , and this is also where Terra and Zidane begin their storylines . Cecil and Bartz fight Golbez here in their respective storylines . While being named The Lunar Subterrane , the stage is clearly the Lunar Surface . The Subterrane is a large arena with a multi - leveled landscape full of cliffs and pits . Quickmove bars extend from the center of the arena outward in three directions , allowing characters to cross the arena quickly . The Crystal Palace and " Lunar Whale " can be seen on the stage ' s background , as well as the Earth . The arena ' s Ω form features more destroyable cliffs than the default stage , and some sections of ground can be destroyed as well . The Bravery pool rises when the landscape is destroyed . The Moon Stone is the battlegen item obtained through stage destruction in this area . " Dissidia 012 Final Fantasy " . The Lunar Subterrane returns as an arena in " Dissidia 012 " . In the 12th cycle , this is where Lightning fought and defeated Kuja . " Theatrhythm Final Fantasy " . The Lunar Core appears as the FMS for Within the Giant . " Theatrhythm Final Fantasy Curtain Call " . The Lunar Core returns as the FMS for several final dungeon themes throughout the series :