Originally Grendel began as a genetic experiment Dr. MacGregor began but had to abandon upon hi exile to South America. Once he began working for Destro, MacGregor tasked several operatives to try and locate his "experiment". Grendel was found in and Irish Prison, he was broken out and brought to MacGregor to see if there was any way to salvage him. MacGregor found that the genetic anomalies he had created in Grendel were more than he could have hoped for. Superior agility, strength, and fighting skills, MacGregor continue but using nanites to further enhance Grendel making him the ultimate killing machine.