You will find Minwu on the top floor of the tower, which is mercifully empty of enemies, and he will open the way to the Ultima Tome. The "Tome" is actually the central orb in a group of five. However, as soon as you grab it, you will be transported out of the tower, so touch the other four orbs first. Each will grant a +10 bonus in one stat to a random Character. Clockwise starting from the northeast orb, the stats boosted are intelligence, agility, strength, and spirit.
Note that once you grab the Ultima Tome, the Cyclone will appear on the World Map, and the World Map and ocean encounters will become much tougher for the rest of the game. Several towns will be destroyed as well, but none that are important this late in the game.
Note that once you grab the Ultima Tome, the Cyclone will appear on the World Map, and the World Map and ocean encounters will become much tougher for the rest of the game. Several towns will be destroyed as well, but none that are important this late in the game.