The Void was created when Robert Reynolds took the Professor's secret formula hoping to get high. Robert Reynolds instantly became the Void, a creature of evil and malice, while another entity was created in his mind to counter him, the Sentry. The Void and the Sentry are linked, as they are technically the same person. No matter how many people the Sentry saves, the Void will kill the same number.
The Void believes he is integral to the Sentry's survival. As the Sentry's power hinges on his emotions, any individual could crush him if the Void were not there to kill them. Once the Sentry found that the Void was a different entity he took the void and threw him into the sun, but the Sentry still fears his return.
