In the early days of New Genosha, most mutants took the concepts of a Sentinel invasion very seriously and many turned to the monarchy for assistance on the matter. Mutant X and ForestFire both gave the speech that they will work on a new countermeasure against the Sentinels. They called upon the assistance of Tony Stark who arrived in no time with the use of his Iron Man armor. Upon his arrival, they worked countless hours on a new design and developement. They later made the first fully functional prototype of the Sentinel Killer.
Resurrection of the SentinelsEdit
By the same year as the establishment of New Genosha; Bolivar Trask managed to escape and get his hands on a secret Sentinel manufacturing plant in New York. After that, he sent a total of 50 Sentinels towards New Genosha. Upon seeing this, Mutant X sent out a new batch of 20 S.K. units and within a total of 5 minutes, the 50 Sentinels sent by Trask were all turned to ash and hit the ocean before they even had a chance to set foot on New Genosha.
Since they proved their worth against Sentinels, the Sentinel Killers have been a major aspect of defense for the mutants of New Genosha.