Mark Booth's History
Mark Booth and his wife
April founded a company called Booth Cybernetics and, at some point, they become obsessed with the idea of obtaining super powers. After studying multiple possibilities, they decided the best course of action would be using Gamma Radiation, with
Jennifer Walters (the She-Hulk) being their candidate of choice to obtain blood samples from, due to her power while still also maintaining her intelligence.
After hacking into Stark Industries to get her blood samples, they proceeded with the experiment. For a few seconds after their first transformation, everything seemed to have worked for both of them, having hulked out while retaining their intelligence. Before long, however, side effects began manifesting. Mark lost his intelligence and
April reverted to her human form while retaining a disproportionately large head.
Mark wrecked the whole laboratory before returning to his human form. Once the dust had settled, they began working on fixing the situation. However, Mark kept transforming whenever they faced any adversity and, eventually, he stopped reverting to his human form altogether.
Still determined to solve the issue,
April discovered that
Jack of Hearts had once absorbed
She-Hulk's radiation. Through unknown means, she then got hold of
Jack and experimented on him, successfully restoring Mark's original skin tone, but not yet his intelligence.
After Mark had an altercation with
She-Hulk in public,
She-Hulk decided to pay
April and Mark a visit at their home. When she got there,
April saw it as an opportunity to experiment on her and told Mark (who was green once more) to seize her.
April was ready to absorb
She-Hulk's radiation when
Jack of Hearts showed up to rescue her.
She-Hulk broke free and started battling Mark, while
Jack confronted
April. In the chaos that ensued,
April accidentally absorbed Mark's radiation, effectively curing him, but inheriting his reduced intelligence and skin tone, referring to herself as
Anathema.