This achievement does not include the Dark Arts battle arena, meaning there are only 2 to complete:
- The North Ford Bog Battle Arena, travel to the "East North Ford Bog" floo flame and head North East.
- The Feldcroft Region Battle Arena - travel to the "Irondale" floo flame and head South West.
To unlock the arena, simply smash the white vases surrounding the area. They are easily spotted using Revelio. There is a counter displayed in the top right corner of how many you have smashed.
Fight through 5 waves of enemies in each to complete the arena.