FF4 DS Sealed Cave Golbez Kain
Continuing the Final Fantasy IV 4 DS Walkthrough Guide, you will need an airship that can fly over lava to reach the Sealed Cave. The last crystal is here, but you need Luca's key from Giott and the Dwarves.
Sealed Cave B1 : Nothing to the west, so head south and down the rope. Further south for a door, which turns into Trap Door. These are tough creatures that lock into a target and then use an instant death ability. You will need to be fast and don't be afraid to use your best abilities here. Near the end of their HP they will turn into another random monster. Head inside this cave now to find an Ether and Kotetsu. Back to B1, and take the lower west path for a Bestiary. West some more to climb up another rope. For completing the B1 Sealed Cave map, you earn 3 Gaia Drums. Take the door in the northwest corner for another Trap Door and a passageway.
Four passages to take in this area. Also, grab the Hi Potion and Ether. The northeast and northwest doors net you nothing in return. Head southeast to Sealed Cave B2.
Sealed Cave B2 : You can go east or south. Choose south, and go east for a Bestiary. The east route leads to a Phoenix Down and a north path. Plenty of doors here. Starting from the northeast, you will find; nothing, Lustrous Sword, Elixir / Fuma Shuriken / Light Curtain, nothing, Save Point, and Kotetsu / Black Cowl. South to complete the B2 map and get 3 Red Fangs. The final door here leads to B3.
Sealed Cave B3 hallway : Grab the Ether in the hallway. Take the southwest exit and there will be another hallway to take. Two treasures in the southeast, a Hi Potion and Phoenix Down. The northwest door leads to nothing, so take the southwest path to B3.
As you travel east, you will see a rope going down at that first hole. First take the northeast path for a Silent Bell and then complete the B3 map for 3 Blue Fangs. The southeast door leads to nothing. Climb down that rope from the earlier, in the middle of the screen.
West is the exit and east is the door - you get two more Blue Fangs for completing the B3 south map. The east door has a Dry Ether and X Potion. The west exit leads you to a Save Point.
Sealed Cave B4 : Just walk around and complete the B4 map for 4 White Fangs. The ropes lead to nothing so just go south to the B5 entrance.
Sealed Cave B5 : You get a Megalixir for completing the B5 map. Just go north and grab the Crystal.
As you head out, the Evil Wall will stop you! This boss closes in on you until it's right up next to you and will then slaughter you. So, this battle is essentially timed. Haste is a must have on everyone if you can, Berserk on your attackers like Edge and Cecil and Kain might be wise too. Jumping with Kain missed a few times for me so I kept going for the sure regular attack. Leviathan is a boon with Rydia, dealing 7000+ damage, otherwise the -aga spells should take off 3500-4000 for you.
Once defeated, you can walk out. Those who have played the original Final Fantasy IV 4 remember that you are betrayed by a friend as you leave - again.