This is a big place. On the first floor, in the upper-left corner is Fire Armor, the door is in the upper right.

On the second floor, a Fire Sword is in the upper left, guarded by a FlameDog, along with the door.

On the third, the door is right above the one you came in.

On the forth floor, there are three doors in the center of the room. Go in all of them. You should find: a Poison Claw, a Fire Shield, an Earth Wrench, and a Wizard Tunic.

On the fifth, there is a savespot and the delta sisters. They are probably the hardest required boss there is. After the battle, go back and save. Unequip Tellah, as he will die.  Tellah will get into a fight with Golbez, killing himself in the process. Go talk to Kain. You will rush off to save Rosa. Both of them now join your party. Equip them. Now go down and fight Valvalis. When you win, the tower will fall, but Rosa uses Exit just in time. It puts you right back at your old bedroom. Kain gives you a key to the underground. Go into the right tower and get all the treasures. Leave the castle. Go south and land at the first island you see; Agart.