Super Sentinel

The Watcher Sentinel, sometimes identified as the Super Sentinel, is a Sentinel variant that is considerably larger than standard Aggressor Sentinels. Like the Enforcers, they are only used to combat large Flood outbreaks, or other considerable threats.

History
Watcher Sentinels were present during the Battle of Shield 0459. They were activated when Shield 0459's artificial intelligence autonomously initiated "Stage 3 Defense Protocols", after large numbers of Flood forms, along with Covenant forces and the crew of the, were detected. The Watchers were tasked with eliminating these targets. The Watchers on the shield world were most likely destroyed along with the entire installation when the star within it went supernova.

Gameplay
They are available as a support unit in Halo Wars. They, like regular Aggressors, are built at the Sentinel Shop. Intended to support anti-vehicle and anti-infantry operations, they are unable to engage aircraft, and require Aggressor escorts for aerial protection. They cost 250 resources and require a minimum tech level of 2 to be produced and count as 2 population. They fire a beam of energy that temporarily prevents an enemy ground unit from attacking and reduces its movement speed. However, the beam does not do much damage by itself.