Oceania, at the end of the game, there’s a bug, can you help?

You can obtain the Sphere by completing a quest located on the small island below the underground world. For this, you need the Amulet of Clairvoyance (which can be found near the Crystal Dragons on the same island) and the Red Orb (which can be found behind the hydras on the same island). Alternatively, it's best to get there using the Fly spell or Dimension Door.