like anjean, oshus is older than 100 years old.
Oshus is the old man from the beginning of the game,or the "grandfather" of the fairy
the sea king is oshus (the grandpa guy who teaches you how to use your sword)
As soon as you start the game you sould go to to Oshus' home right away. If you're far away, you can go to Mercay Island. His home is just across the bridge
first (if you havn't already) try to take the cave to town, after that go and talk to oshus. then go into his storage room, and the answer to the "riddle" is 7. then you get the sword :) :) :)
Go to Oshus's house, and just to the right of his house is a cave that serves as his storehouse (where you got the first sword). There is a tree just outside the storehouse. Dig directly in front of it to discover the treasure.
you will have to get 3 pure metals and give it to zauz when the blade's finished, go to the ocean king's(oshus) house and he will combine the blade and the hourglass together and there you go! you got the phantom sword
haw to get to belom
Before Link used it (after the fire temple) Oshus used it. SPOILERS: Oshus was using it to look after Bellum after he was defeated in a battle with him.
you have to draw a seven on the sign
Strike them, that's all there is to it. Of course you must have your sword first. You can obtain it in the cave next to oshus's house. Draw a 7 on the board next to the door and grab the sword inside the chest.
Now, do you mean towards the end of the game? If so, drive your boat toward it to board. then comes the boss battle. If you mean when you first find Tetra, go back to Oshus... then take it from there...
After you obtain all the pure metals and forge the Phantom Sword with the help of Zauz and Oshus, you must continue to the bottom floor of the Temple of the Ocean King where you got the last sea chart. Then you kill all the phantoms that guard the door at the centre and go through. Up the stairs is the main villain in the game, Bellum.