Legion Invasions are world events that occur on a rotating schedule across the Broken Isles. During an invasion, you can earn Bronze, experience and special transmog sets.
Legion Assaults appear in one of the four leveling zones on the Broken Isles: Azsuna, Val'sharah, Highmountain, or Stormheim. Each assault remains active for 4h, then goes on hold for 3h before the next one begins, repeating every 7h.