Odin/Raiden Magicite

Upon arriving in the first room of the Cave to the Ancient Castle, find two chests: one to the east with a Hi-Ether and one to the west with the Wing Edge weapon for Locke.

Go back east from the Hi-Ether chest and through the door to find another chest containing the Master Tonberry.

Master Tonberry Strategy: Cast Sleep and Slow on the Master Tonberry. Use Libra to identify its elemental weakness and exploit it with magic or Espers. If its weakness is Earth, Wind, or Water, use non-elemental magic like Flare or Ultima. If you cannot exploit a weakness, cast Vanish on your party to mitigate physical attacks. Attack the Master Tonberry ONCE to wake it up. Wait for Barrier Change (occurs every 10-20 seconds), then reapply Sleep and Slow and resume attacking its weakness. Magic will not wake a Sleeping target. If it awakens, reapply Sleep. Ultima can also be used to defeat it quickly.

The Master Tonberry can drop a Gladius, the fourth most-powerful Knife in final fantasy vi.

After the Master Tonberry battle, return to the previous area and go west to where you found the Wing Edge. Use the nearby door.

Follow the path to find a chest containing the Death Tarot.

Go back and find a path in the western wall. Take it and go northwest to find an alcove in the northwestern wall to reach the next area.

Head southwest of the stairs to find an X-Potion.

Go far south of the stairs to find the Magicite Shard.

Go downstairs to find a Save Point. Use it and proceed up the next staircase to find the Ancient Castle.

In the Ancient Castle, head to the entrance and go into one of the two black doors west of the main doors. Open the chest to fight the Samurai Soul.

Samurai Soul Strategy: Use Confuse at the start of the fight. The Samurai Soul may then use Assassin Blade on itself, leading to its defeat. If it uses other attacks, reapply Confuse. Edgar's Noiseblaster and Cait Sith are also effective for inflicting Confusion.

The Samurai Soul drops the Master's Scroll, which allows four non-missing attacks per weapon, though the power of each attack is halved. This is best used with the Ultima Weapon and another powerful weapon for eight attacks (double damage), but it prevents the use of a shield, lowering defense.

After the Samurai Soul battle, exit the castle and go east of the main doors. Go through and pick up the Punisher from a chest.

Exit again, go through the main doors, and head north to find Odin.

Before interacting with Odin, go east and through the left black door to find the Blizzard Orb and the Gold Hairpin.

Backtrack to Odin's statue. Examine the Odin statue to obtain the Odin Magicite.

Go east and south from Odin's statue to find a path to the queen's room. Examine the bucket for an X-Ether.

Examine the sparkly thing on the bookcase to read the queen's diary.

Stand on the eastern throne, face it, go five steps south, and examine the tile to reveal a hidden staircase.