Chaos Axe is better found in the Fissure of Woe, otherwise known as FoW or Fissure. You can get there from the Temple of Ages (ToA) in Kryta. You must be ascended and pay 1 plat to go in.
If you don't understand any of those terms, continue with the game, you're not ready for FoW yet.
you can get chaos axes in the fissure of woes (not sure about UW never been there), you can get there by going to temple of ages when your area (korea, america, or europe) has favor of the gods
