OKay here is what i found so far. Pick up the notes as you go through. There are three seperate dungeons. Each one is tougher than the previous.

At the end is a group of people in a "town" who collect various pieces of olthoi to fashion into weapons. Spear, unarmed, bow, atlatl, axe, but didnt see sword.

None of the portals are recallable, but you earn exp from the notes you picked up my first note was 200,000k second one was You've earned 3,906,245 experience.

good luck!!