Use Apocalypse to kill 50 enemy units or structures in a single mission.
Complete “The Reckoning” mission in the Heart of the Swarm campaign.
Complete the Zeratul storyline in the Wings of Liberty campaign.
Complete the “Echoes of the Future” mission with Zeratul killing 50 Zerg units on Normal difficulty.
Destroy the Loki in the “Engine of Destruction” mission on Normal difficulty.