Dead Zone (location)
From Dragon Ball Encyclopedia, the ''Dragon Ball'' wiki
The Dead Zone (デッド ゾーン, Deddo Zōn) is a void of darkness that Garlic creates to suck people in and trap them, leaving them to float through an endless darkness.
Dragon Ball Z
During the Garlic Jr. Saga, Garlic Junior reopened the Dead Zone in retaliation for his dark plans being foiled (Kami and Mister Popo had broken his curse on the people of Earth by using the Sacred Water). Piccolo Junior, Kuririn, Kami, and Popo were nearly sucked into the Dead Zone, but Son Gohan destroyed Planet Makyo, thus draining Garlic Junior's fearsome strength and causing him to be sucked into the Dead Zone once again. By the end of Dragon Ball Z, (though it was never referenced following the Garlic Jr. Saga, save for maybe Piccolo's line about the Heavenly Realm being completely ruined again) he still lived, immortal and trapped within the Dead Zone never to escape.
In Dragon Ball Z: Dead Zone, Garlic Junior opened the Dead Zone in an attempt to suck in Son Goku and Piccolo because he knew that despite his immortality, he could not beat them. Gohan was able to resist its suction, however, and knocked Garlic Junior into the Dead Zone. He remained in the void for about three years until Planet Makyo was close enough to Planet Earth to allow him to escape.