The Theron Sentinel comprises the elite of the Hollow; stronger, faster, more intelligent, better armored, and better armed than the Locust Drones. The Theron Sentinel operates a commando unit, excelling at dealing with situations as they come up. Probably considered the "Centurions" of the Locust Army, the Theron Sentinels are powerful foes indeed, the Elite and bulk of discipline of the Locust. The Therons are usually held in reserve until the situation calls for them, but their posting on the battlefield is decisive and generally indicates that the Locust need a mission accomplished, and deem it important enough to trust their best to deal with it. Therons are usually field commanders and strategists, as they are far more intelligent and cunning than the average Drone.
Amongst the Theron Guard, there are Therons who prove far more brutal, cunning, ruthless, and resourceful than their fellows. These eventually become Theron Sentinels, who serve as squad leaders and sergeants for Theron Guard units, and who act as bodyguards for higher-ranking Locust. RAAM in particular had a contingent of several who served as his personal guard; these were killed, along with RAAM, in Act 5 of Gears of War.
Particularly skilled Theron Sentinels may become Palace Guards, who protect the Locust Queen's Palace. Theron Sentinels are easily identified by their red-chased armor, which most likely signifies their importance. Like regular Theron Guards, they usually wear a helmet that protects their heads and obscures their faces, usually leaving only their mouths visible. Though this helmet offers some defense, it cannot protect the Sentinel from headshots.
Like the other Therons, the Sentinels favor the Torque Bow. Several can also be found using Hammerburst Rifles, Lancer Rifles, Boltok Pistols, and Gnashers. It's worth noting that Theron Sentinels are one of the few Locust that have the common sense to pick up dropped weapons in single-player. If a downed Locust drops a weapon such as a Longshot Sniper Rifle or Gorgon Pistol, the Sentinel may run over, pick it up, and use it.
Theron Sentinels, like all Therons, are well known for their sinister, whispery and sibilant battle cries and hiss-like inflection when speaking.
A notable Theron Sentinel that possessed great skill and power, was RAAM, before he became General.