The World Egg

You discovered a magical artifact resembling a huge egg containing a portal to a strange world. After some experimentation you have learned that the egg actually creates these worlds, about once a week. The type of world that is created can be somewhat shaped by focusing your thoughts for the week leading up to each world's creation. The egg seems to take in these influences and shape the new world accordingly. You have seen lifeforms in these created worlds but haven't stepped inside yet.