StarCraft: Protoss: Stalker Expansion Set

The fall of Aiur showed the Nerazim that more than stealth was required to defeat the zerg, and thus they developed the Stalker - a war machine controlled by the shadow-essence of a Dark Templar warrior fused into a metal body.

This ranged strider also possesses the ability to displace itself and reappear elsewhere, making them ideal at ambushing or generally engaging only on their terms.