Purchase all Mercenary contracts.
Complete the “Echoes of the Future” mission with Zeratul killing 50 Zerg units on Normal difficulty.
Complete the “Ghost of a Chance” mission using Dominated units to kill at least 15 enemy troops on Normal difficulty.
Complete all mission objectives in “The Gates of Hell” mission.
Complete the “Supernova” mission on Normal difficulty without losing a unit to the wall of fire.