StarCraft: Brood War/Dark Origins

By completing Zerg Mission 9 (The Reckoning) in 25 minutes, and new level is unlocked: Dark Origins.

After killing Razagul, Zeratul feels very guilty. However, he might be able to defeat Kerrigan by finding Artanis. He senses Protoss energy signatures is the Dark Mood, and goes there.

In game, the player gets two dragoons, Zeratul, and FOUR dark archons. The player is supposed to mind control a large number of units.

In the end, Zeratul finds that Samir Duran has been making these hybrids. Zeratul asks whether Kerrigan authorized this, but Duran says that he serves a greater power.

Gamers think this refers to the Xel'Nega.