- Obtain both original glaives from the original Black Temple on a Warrior, Rogue, Death Knight, Monk, or Demon Hunter
- Equip both at the same time to obtain this achievement
- Kill Illidan in the Timewalking version of Black Temple on any character (in a premade group, leader talks to Vormu to enter raid)
When Illidan dies in step 3, you will get this achievement, unlocking the transmog.
Theses steps have to be in this order. There are no exceptions.