Observer (StarCraft II)

"Ah, this faithful Observer has kept watch since the evacuation. Its abilities will certainly prove useful now."

- Zeratul

The observer reprises its role as a stealthy detector.

Legacy of the Void Campaign
The observer is not available during the campaign as detection is never required.

Co-op Missions
Artanis and Karax are able to build observers in Co-op Missions. In Patch 3.1, Artanis' observers gained the Surveillance Mode ability

Development
In a September 2008 build of StarCraft II, the observer did not require an observatory to build, making it available earlier in the tech tree than in StarCraft. It was upgraded at the null circuit.