When the Celestials experimented with the Skrulls, they created two sub-species of them: Dire Wraiths (the equal of Deviants for Skrulls) and their perfect genetic counterparts, the Prime-Skrulls (the equal of an Eternal for Skrulls). However, the Prime-Skrulls evolved way to fast and the Celestials regarded this as a problem and destroyed them all. Somehow, the young Prime-Skrull, whose name is never revealed, managed to survive. In 1947, he was discovered by other Skrulls who tried to hunt him down. Having no other solution, he tried to flee to Earth, being pursuited by a regular Skrull. The both of them crash on Earth and were studied in Wright-Patterson Air Force Base. There, Dr. Caitlin Maddox managed to obtain an enzyme that could speed up human evolution, in the same way the Prime-Skrulls had hyper-evolved. This enzyme was derived from the Prime-Skrull´s adrenaline with the side-effect, that it also made people immune to the Black Legacy.