The final area is a real pain. Four elemental dungeons, with midbosses + bosses, and once you go to that chapter you lose any chance of restocking on potions.
There are some real aggravating parts that took me far too long to figure out, so for this topic's benefit, here they are:
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When you are at a castle after killing the evil sorcerer, after a scene, all hell will be breaking loose at night. The lower-right corner is where you will need to be to trigger a boss and the next scene.
In this scene, you'll need to make your way up the castle, flipping all the switches you find - make sure you start by going to the right, as at the top of that section, is a flip switch that does... something. I don't know, but it looks important.
After rescuing the green-haired girl going further up will bring you to a chamber where you fight a trio of assassins. If you are good, killing the last one by the crack in the wall will reveal two chests. This is usually too hard to pull off, so don't worry.
The green-haired girl will be outside and tell you something. Go just outside the doorway and examine the torches to open the locked door.
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In the next scene, in the assault on the castle, examine all of the shields; on two of the shields (opposite sides of the castle), they can be moved to reveal passageways.
After beating the hammer boss, return to the knight towards the beginning of that screen. He will give you a mirror which reveals false walls. There is a false wall right before the hammer boss's room. You can tell because the tiles are different than normal wall tiles.
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On the mountain leading to the magical realm, a winged guy will blow you away from the gate. You first need to talk to a boy selling stuff (this is your last chance to buy spells and potions, so make it count). Talk to him a few times (maybe having important things in your characters' inventory?) and something will trigger to allow you to approach the winged man, who will release a tiger. Defeat the tiger and confront the winged man on the southern-right corner of the map.
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In the wind realm, take the teleporters until you see a fairy, and have Melvy catch her. Afterward, cast a green barrier spell on yourself to make it past the green tornado in the center. You will have to do some platforming to reach the boss.
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In the earth realm, you will need to have the knight midboss be charging at you to hurt him. Use Rhun and fire projectiles as he does so.
