Instructions
Play through the game until you enter the tomb. This event occurs naturally in the course of gameplay; you cannot accidentally miss it.
Surf east on the southernmost edge of Pacifidlog until you reach the first engraving.
Read the first passage, which translates to "GO UP HERE." Your character will automatically travel to the next chamber.
Dive into the water until you reach the next engravings. Read the stones, which translate to "DIG HERE." Return to the previous wall and use any of your Pokemon with the Dig move.
Travel to Mr. Brinley's house, which is the largest one on the island. Surf south until you reach an island. Head north and read the stone, which translates to "STOP AND WAIT. WAIT FOR TIME TO PASS TWICE." Do not push any buttons until a door appears. Enter it.
Cross the desert on Route 111 and enter the ruins. Push "Right" twice, "Down" twice and then use any of your Pokemon with the Strength move. This reveals a door to the final chamber.
Walk into the very center of the room. Use any Pokemon you have with the move Fly to reach the end of the tomb.