Theta Sentinel

A highly advanced AI lifeform and one of the later generation models of the self-sustained Sentinel Program of the Man-Machine Supremacy, the Theta Sentinel came into existence during the ninth lifetime of Moira MacTaggert, where they were utilized as a hyper lethal hunter of Mutants during the Human-Machine-Mutant War. Under the leadership of Nimrod the Lesser, the Machines would rapidly outpace the human race and lead to their subservience, while driving the Mutant population to near extinction. After over 100 years of War, the majority of the surviving Mutant population fled the Sol system for Shi'ar Space, leaving only a small force of Mutants on the planet under the leadership of Apocalypse.

At least one of the Theta Sentinel models was present during the final stages of the Man-Machine Supremacy's war, and was thrilled to take one of the last remaining members of the X-Men, a Black-Brain Telepath named Cylobel, captive- looking forward to personally torturing her for information. Partway through the torture, Rasputin, another member of the final X-Men, arrived to destroy the Theta Sentinel. Ultimately her efforts were for naught, as she was overwhelmed by Sentinel forces, and Cylobel was taken back to Nimrod, who had her killed and assimilated into a digital database of Mutant minds.

Tri-Sentinel Build-A-Figure (2021)
The Theta Sentinel made its figure debut as the Build-A-Figure of the first dedicated X-Men wave released in early 2021, based entirely on the House of X and Powers of X miniseries. The figure is an entirely original sculpt based on the concept sketches from artist R.B. Silva for the character's singular appearance from Powers of X #1. Due to the design's top-heavy torso, spindly limbs, and small feet, the figure has notable balancing issues, while the necks for each of the heads are pre-posed and fit somewhat poorly into the ball sockets of the torso, leaving them lacking in their range of motion and prone to popping out.

As a Build-A-Figure, the Theta Sentinel is broken up across six of the wave's seven figures, with Wolverine including no piece. Its three heads were included alongside Magneto, the torso came included with Omega Sentinel, the arms were split among Professor X and Cyclops and the legs were included with Marvel Girl and Moira MacTaggert.

The figure is erroneously identified as a Tri-Sentinel on the packaging, a mistake the Hasbro would later issue an acknowledgement of during one of the subsequent "Fan First Friday" livestreams a few months after the release.