It’s more than just the dark side of the Sentry. Introduce in Sentry #1 (2000) by Paul Jenkins and Jae Lee, the origins of the being what would become known as the Void is unknown. It is believed that it may be the Angel of Death that killed the Egyptian children at the end of the Seven Plagues of the Old Testament. At some point, it bonded with Robert Reynolds when he took the formula that turned him into the Sentry. Sentry became a hero to the people while the Void would become his arch-villain, killing the Sentry’s sidekick, Scout, as well as millions of people. Sentry began to believe that this was a part of of his psyche and would work with Reed Richard and Dr. Strange to make everyone forget who he and the Void was.

While he would return a few times with the Sentry, Sentry would return to full heroic when the New Avengers confronted him along with the X-men and Inhuman. After a battle with the team, Sentry believed the Void was defeated and joined the New Avengers. When Yelena Belova attacked the New Avengers during the Cage wedding, she absorbed Sentry powers including an aspect of the Void which drove her mad, but she was killed by her handler’s soon after. When Norman Osborn became the head of Superhuman activities, he gave Sentry an altered formula that brought out the Void, who agreed to work with Sentry. However, the Void went out of control during the Siege of Asgard and was sent into the sun. Sick of constantly reviving with Sentry, he would leave Sentry and travel to the White-Hot Room.

At some point, Dr. Strange had captured the Void and locked him in his Sanctorum. Strange would use the Void to defeat Loki, who had stolen the Sorcerer Supreme role from Strange. Sentry would eventually be revived by the Apocalypse Twins, so the Void was locked up in his psyche again. The two sides of Sentry would eventually merge into a Dark Sentry and would fight the Agents of Wakanda. Sentry would seek the aid of Reed again to separate him from the Void, which resulted in the dark entity being trapped in the Negative Zone. He would escape into the Cancerverse, where he took the appearance of Sentry to lead their army to fight the Prime universe. They were defeated by an army of cosmic heroes, but Sentry had to merge with the Void again and remain in the Cancerverse. Sentry was later summoned to help in the battle again Knull, but he was killed, and the Void would submit to Knull. A Cosmic empowered Eddie Brock eventually defeated Knull when he was plunged into the sun, and it is believed the Void died as well……but we know that it will be back.

I don’t think anyone wanted a Void figure as many just assume he is only the dark side of the Sentry. None the less, Hasbro announced a Void figure as a BAF in his own wave.