Final Fantasy II/Mission to the Pandaemonium

A tough explanation
Firion and company, along with Leon, will return to Fynn. Upon seeing Leon, Hilda will demand to know what has happened. Firion will explain that the Emperor has returned from hell. Maria explains how Ricard sacrificed himself so that they could escape. Then she recounts all the others who have passed trying to aid them. Leon will then agree to join your team at Maria's request.

Return to the audience chamber and speak with Princess Hilda. She will mention the term Jade Passage which you can choose to learn. If you ask Hilda, Gordon, and Leila, you can piece together that the Jade Passage is essentially found in a small lake to the east of Mysidia. When you exit from Fynn Castle, you will find Cid's airship waiting for you outside.

Leon the black knight
Leon's default weapons are an axe and a sword. Despite his proficiency, if you've stuck to the default weapon specialties for the main chatacters, give the best the axes to Guy and the best swords to Firion. Equip Leon with the next best axes and swords, or give him the best staves and spears, that would be otherwise unused.

Detailed analysis of Leon's weapon skills:
 * Axes L9: it's better to leave the axes to Guy, who can make better use of the white-spellcasting Rune axe;
 * Swords L8: it's better to leave the swords to Firion, who can make good use of the black-spellcasting Masamune sword;
 * Spears L7: after Leon joins you, soon a white-spellcasting Holy spear will be found, although Leon is more proficient with Black magic;
 * Staves L6: you should already own two black-spellcasting Mage's and Wizard's staves plus a Healing staff, so this is the choice;
 * Daggers L5: none have special effects, so ignore them;
 * Slings L4: it's better to leave the bows to Maria;
 * Shields L3: every character should use a shield to improve his/her evasion;
 * Karate L2: this is Leon's lowest skill, ignore it.

Equip Leon with a few black and a few white spells, just to improve his spell casting abilities related to the special weapons he can use.

The Jade Passage
Hop in the airship, and make your way to the Mysidia region. Sure enough, if you travel east from the town, and just a bit north, and follow the land as it juts out into the ocean, you will eventually notice a small lake near the end of the land mass. Land your ship and step towards the lake to enter the Jade Passage. Once inside, you will be facing, quite naturally, the toughest enemies you have faced so far.


 * Floor 1: There are two chests to obtain on this floor, one far to the right of the entrance containing the Diamond Mace, and one far below the entrance containing a Hellfire. However, the creatures you will encounter in the process of retrieving them will give you a good idea of what you're up against.  In particular, the Great Malboro and Abyss Worms are not to be taken lightly, with the amount of status ailments and full party attacks they can inflict.  The exit to the next floor can be found in the lower right corner.  Ignore all other doors.
 * Floor 2: Final Fantasy II boss Blue Dragon.png There is a very high likelihood that you will be attacked by White Dragons as you explore this floor. Be prepared to counter with high level Fire spells.  Ignore all the doors on this level except for the exit in the upper right corner.  There are three chests, the first of which is directly above the entrance.  Open it for another Hellfire.  Then follow the water to the right, and after it heads down, check the short passage to the right for another chest containing Antarctic Winds.  But the best treasure of all can be found by heading down until you reach the bottom, and exploring to the left.  There you will find a chest containing the Cat Claw weapon (good for anyone who is experienced in fighting bare-handed), but it is guarded by a Blue Dragon.  Blue Dragon's specialty is Thunder-based attacks.  Therefore, its weakness is to Poison based attacks, so cast Scourge if you have it.  (The Blood Sword is also effective against this dragon.)  Then follow the bottom back to the right, and up the right side of the floor to find the exit.
 * Floor 3: Final Fantasy II boss King Behemoth.png This floor is fairly linear, and forces you to walk beneath waterfalls which sap a little of your health with each step beneath them. As is usually the case, ignore all the doors except for the very last door you reach in the lower left corner of the floor.  There is one treasure chest to collect along the way, and it contains the Rune Axe, but this powerful weapon is guarded by an equally powerful creature: the King Behemoth.  It's a more powerful version of the Behemoth you faced way back in the Coliseum.  It happens to be weak to Poison based attacks, but it's also weak against the Blood Sword, so it's a good idea to equip that weapon before you examine the chest.  The King Behemoth can land some incredibly powerful attacks, easily doing damage in the thousands to even very leveled characters.  Protect and Blink can go a long way to help you survive this battle, as can Haste and Berserk.
 * One thing to note before you leave this floor: if you examine behind the waterfall at the very bottom of the map, you'll discover an invisible salesman that actually sells some of the strongest Black magic in the game which can't be purchased anywhere else! You can buy a Death Tome or a Berserk Tome for 10,000 Gil each, Haste for 20,000 Gil, and Flare for 40,000 Gil.  Stock up if you have the money, and then proceed to the exit in the lower right corner.


 * Floor 4: Final Fantasy II boss Red Dragon.png There is a lot of important treasure to discover on this floor. Two can be found in chests out in the open, but three are behind a door found at the top of the room.  The first chest can be found on your way to the top, and contains a Betrayal Fang.  When you reach the door at the top, enter inside to find the Dragon Armor and the Aegis Sheild, two very strong defensive pieces of equipment, and the Holy Lance, a weapon you should consider giving to Leon.  Back outside, head to the right, and you'll find the second chest.  Inside, you'll find Yoichi's Bow, one of the best bows in the game, along with a forced fight against a Red Dragon.  As usual, the dragon is weak against the Blood Sword, and since its attacks are Fire based, it is also weak against Ice attacks, so cast Blizzard liberally.  When you are finished, proceed through the door in the lower right corner to access the next floor.
 * Floor 5: When you arrive on this floor, there is a sign posted by the entrance which informs you that the path you are on leads to hell (or some variation of that depending on which version you are playing.) Throughout this floor and the next, you will be attacked almost exclusively by Chimera Sphinxes, along with the occasional Green Dragon.  This floor is linear, and winds around a pit.  There are three chests along the way.  The first and last contain Hi Potions, but the middle chest near the top (ignore the nearby door) contains a Protect Ring, which increases a player's defense against instant-death magic.  Give this to any individual who is responsible for reviving fallen members of your party.  Then make your way around to the door in the lower left corner.
 * Floor 6: The final floor is barely a floor at all, containing just a small passage which leads you to a warp tile. This warp tile will transport your party into the Pandemonium fortress, the one which rose from the rubble of Palamecia when the Emperor returned.  Be advised: there is no turning back from this point.  If you took substantial damage from any of the forced fights, or find yourself lacking in any particular items, now is your last chance to Teleport out of the dungeon to heal and stock up.  Once you pass through the warp, that chance will disappear.

Pandaemonium
You've reached the castle of Hell known as Pandaemonium (which is the Greek for "all demons") As the final dungeon of the game, you will be facing the most powerful creatures that the game has to offer. Among the strongest that you should watch out for are the Death Riders. They sometimes appear with other enemies such as Devil Mantises, or a Mythril Golem, but they should always be your first targets, as they can do well over a thousand hit points of damage with a single hit. They happen to be weak against Fire, so use a high level Fire spell if you have one available.


 * Floor 1:There are no treasures to find, or branching paths to consider. The floor simply takes you all around the outside until you reach the top, and then down through the middle until you find the stairs that lead to the next story.  In the process, you will begin to encounter Pandaemonium's fearsome inhabitants.  As explained above, Death Riders are the biggest concern.  The Lamias and Mantises should present less of a problem.  Make your way to the stairs as quickly as possible.
 * Floor 2: There's only one chest to discover on this floor, and it contains an Ether. After walking down to the bottom of the floor and then climbing up a narrow staircase, be sure to walk all the way to the top to find the chest before descending down the next narrow staircase to the left.  Then follow the path on to the warp tile that lead to Floor 3.  In the process, you may begin to be attacked by Beast Demons and Mythril Golems.  These golems are weak against Lightning-based attacks.
 * Floor 3: When you arrive, head down first to discover the only chest on the floor, which contains an Elixer. It can be found below and to the right of where you arrived.  Once you collect it, return to the warp tile and head up above it before turning right.  Once you do, there are a few ways to reach the next warp tile in the lower right corner, including a false wall to the right of a narrow corridor.  You may encounter the panther-like Coeurls in large packs on this floor.  They don't do a lot of damage, but they're Blaster attack is capable of stunning your characters.
 * Floor 4: When you arrive on this floor, you will start near the lower left corner. Above you will four doors.  These doors lead to doors on other floors.  Those doors lead to a considerable amount of great treasure in the form of powerful equipment, but only one door leads you on your way to the next floor, and that's the third door from the left.  Save that door for last and visit the first two on the left and the door on the far right first.
 * Floor 5a:Take the door on the far left to reach the left side of Floor 5. Follow a path up the left side that leads up to the top.  There are several false walls here.  Even if you think you've hit a dead-end, test the walls to check.  You're very likely to encounter Devil Wolves and Ice Lizards on this floor.  The first chest that you discover near the upper left corner contains the Genji Gloves, but it's protected by a monster.  Namely, the zombie version of Borgan who you defeated earlier.  Now that he's undead, he's vulnerable to Fire and Cure attacks.  Final Fantasy II Masamune.png You should be able to do away with him quickly, and the equip whoever has the lowest defense with the gloves.  Then proceed to the right and follow the path that sticks close to the top of the floor.  When you reach the upper right corner, it may appear that you've hit a dead-end.  However, one of the most powerful pieces of equipment in the game is contained in a room whose entrance is hidden by a false wall.  Push against the right wall, and you should find the secret room with the chest.  Open the chest to find the Masamune.  If you've trained Firion in swords, definitely give this one to him.  There will be no monsters guarding the legendary blade, but the whole room has a high encounter-rate for very powerful enemies such as Blue Dragons, so don't stay too long.  Once you obtain the Masamune, you have no alternative but to retrace your steps and return to the fourth floor.
 * Floor 5b:Final Fantasy II boss Tiamat.png Final Fantasy II boss Iron Giant.png Now take the second door on Floor 4 to arrive near the lower left corner of Floor 5. Follow the shorter, but no less twisty path to the remaining treasure chest in the center of the floor.  This chest contains the Genji Helmet, and it is protected by the powerful creature known as Tiamat.  Tiamat, like its Dungeons & Dragons namesake, is a multi-headed dragon that can use entire-party attacks of every possible element.  To protect yourself, do the standard practice of casting Protect and Blink.  Use of the Blood Sword is recommended, as is casting Flare.  Improve physical attackers by casting Haste and Berserk.  Defeat the creature to obtain the helmet, and give it to whoever has the lowest defense.  While walking through the fifth floor, you may also randomly encounter the Iron Giant.  This boss-level creature is weak against Thunder and Ice, and is capable of dropping some of the most powerful equipment in the game if you defeat it (although it won't always do so.)


 * Floor 6b: Final Fantasy II boss Beelzebub.png As explained above, the third door leads to the warp tile that takes you to the final floors above, so check the fourth door first. It drops you off in the lower right corner of the sixth floor, at the bottom of a very narrow path to the top of the floor where you will find a chest.  The chest contain the Genji Armor, and it is protected by the creature known as Beelzebub.  Unlike many other bosses, Beelzebub is particularly well versed in Black magic.  As a result, the protective spells of Shell and Wall may be a bit more practical than Blink and Protect.  He has no weaknesses, so boost your physical fighters with Haste and Berserk, and use Flare until he is defeated.  Then return to the door below.
 * Floor 6a: Final Fantasy II boss Astaroth.png Finally, take the third door. Follow the path it leads you to until you reach a chest in the center.  This chest contains a Ribbon, a powerful item which can protect you from special attacks.  It is guarded by the being known as Astaroth.  Like Beelzebub, Astaroth wields magic, but the most powerful forms of magic like Death and Drain.  Casting Wall and Shell is even more valuable in this fight.  Beyond that, this fight will be a longer, more drawn out version of the fight you had with Beelzebub.  After he is defeated, equip one of your characters with Ribbon if you like, and then continue on your way to the left through the chamber until it leads you down the left side to the lower left corner of the floor.  There you'll find a warp tile that leads you back to Floor 4.
 * Once back on Floor 4, simply walk up to the top and then across to the left to reach the warp tile that leads to Floor 7.


 * Floor 7: This floor is more straightforward like the early floors. It contains one chest close to the entrance which contains Sage's Wisdom.  After you collect it, all that's left to do is follow the path through the floor in a clockwise direction until you reach the warp tile in the lower left corner of the map.
 * Floor 8: You arrive in the lower left corner. The exit is in the upper right corner.  However, there are two chests, one in the upper left corner which contains an Acid Phial, and one in the lower right corner which contains Hellfire.  Getting them is optional, and will force you into more fights.  Consider your health and items carefully.  Remember that you can hit people with the Healing Staff to restore health.  Any black magic user should be using Osmose on spell-casting enemies to restore magic points.
 * Floor 9: This is one of the odder floors in the castle. It's pretty much a wide-open square.  You arrive near the center of it.  Aside from being able to walk anywhere in any direction, the only notable feature of the floor is the exit contained in the lower left corner.  Roundworms are powerful creatures that you may encounter here, but you can also encounter boss-level creatures like the King Behemoth here, so be on guard.
 * Floor 10: You've reached the top floor, where the revived Emperor awaits you. Don't dawdle on the floor, as you can still be attacked by very powerful creatures.  Head straight up to face the Emperor.  Before going into battle, give every character at least one Ribbon or Protection Ring to significantly reduce the chance that the Emperor instantly kills any of your characters.  If you have the Blood Sword and wish to make the battle considerably easier, equip the sword now.  All of your preparation has been for this moment.  When you're ready, speak to the Emperor to initiate the battle.


 * Final Fantasy II final boss Emperor.png The Emperor has a suite of attacks that he will use against you, including status altering attacks like Curse, and casting Dispel to remove any of the magic buffs that you cast throughout the battle. His standard attack drains your hit point to replenish his own, he can cast high level Flare spells, and a unique entire party attack called Starfall.  Naturally, you'll want to start out casting Protect, Blink, and Shell or Wall.  Cast Berserk and Haste on your primary physical attackers (especially anyone you gave the Blood Sword to.)  Remember that you can cast Berserk on characters multiple times to boost their attack even higher.  Cast high level Flare and/or Holy as often as possible.  Unfortunately, the Ultima spell won't really be too useful unless you've managed to reach high levels in nearly every weapon category.  Be sure to assign someone to the task of healing and reviving anyone in need; don't leave party members out for long as losing even one of you team can give the Emperor an advantage.  The Emperor has 10,000 hit points.  If you do equip and use the Blood Sword, this battle can be surprisingly short.  If you don't, it might be frustratingly long.  It may even take you a couple of tries, depending on how your luck goes.

If you successfully defeat the Emperor in battle, you will then be presented with the ending and the credits. Congratulations.