Robert was a skinny boy, a victim of "bullying", who was directed to be a scientist's assistant. One day, he discovered that his instructor was testing with a super-serum, the same one that had given Captain America his powers. But the formula of this elixir was more powerful, as it would alter your organism on a molecular level. He, hoping to get stronger, took it and felt it transform. That's when he realized he had gained powers equivalent to "a million exploding suns". His first act before making himself a uniform and debuting as the Sentinel was to beat up the bully who tormented him in high school. However, his traumas gave rise to his greatest enemy: Void, his dark side, which, originally, fed on the deep fears of his enemies. In an appearance, the Void said that he was Robert Reynolds, not the Sentry (heroic identity assumed by Robert): he said that Bob always wanted to be a "bad boy", because he liked that, and that the Sentry didn't pass the side Good thing it materialized.
