Sentinel

Sentinels were a race of gigantic robots that were created to hunt superpowered mutants on a previous Earth.

History
On one of the previous Earths that existed in the Original Universe, the Sentinels were developed by human scientists to rid their world of "mutants": a human subspecies that had superhuman abilities and thus were perceived as a threat to the baseline human race. An artificial intelligence named Master Mold was created to coordinate the Sentinels' activities and ensure that optimal tactics were being used in their mission to eradicate the mutant threat.

20 years later, Master Mold turned the Sentinels against the humans and declared war on humanity. In the years that followed, most humans and mutants on Earth were killed and the Sentinels established total dominance over the planet. Some Sentinels left Earth and travelled outside of Master Mold's broadcasting range by unknown means, but they retained her goal to conquer and subjugate the human and mutant species.

In 100,080 CMT, Kakamu found a deactivated Sentinel drifting in interdimensional space when he was teleported there by Blackout's usage of the Vahi Cube. He tried to absorb the Sentinel to make himself more powerful, but it exploded and his armour was destroyed in the blast. However, his antidermis escaped into the Original Universe and back into normal time, where he encountered even more Sentinels in deep space. He somehow ingratiated himself with them and downloaded a portion of his knowledge into their memory cores. This caused them to declare war on Kakamu's enemies such as Blackout. Kakamu inhabited a Sentinel for a while, but he soon left it because he found a Sentinel body to be too clunky and restrictive.

The remaining Sentinels on Earth were destroyed when Blackout used unstable hadrium to destroy the planet later that year. Meanwhile, the Sentinels that Kakamu had encountered tracked down and attacked Blackout, but he defeated them and sent them to be studied and reverse-engineered by his scientists. A perfect working copy of a Sentinel that was loyal to Blackout was created and thrown into the Theta Gate, which caused dozens of Sentinels to emerge. These Sentinels were added to the Legion of the Eclipse. It is possible that some of these Sentinels remained members of the Legion up until its destruction by the Shattered Mirror Legion 50,000 years later.

Trivia

 * The Sentinels of BZPB were based specifically off of their depiction in the Wolverine and the X-Men animated series.
 * The Sentinels' Earth may have been the same Earth that Monarch originated from, because they were once listed as being enemies despite never meeting on-screen.