Possibly surviving from the previous universe, the Dweller originates from the Everinnye dimension, but turned his back on his fellow denizens - such as Nightmare - by following the Way of the Shamblu, disembodying his head and existing in physical form. From the Halls of Fear dimension, he generates fear and doubt but avoids the notice of those who might oppose him. Over 20,000 years ago, the Dweller fed off the fears from the Human-Deviant wars, but the sorceress Zhered-Na invoked the powers of Agamotto and Valka and sent him into mystic slumber. When the Great Cataclysm sank Atlantis, the Dweller used the resultant worldwide fear, imbuing some of his consciousness within it, creating D'spayre to act as his agent. Though he remained trapped, the Dweller gained power from fear throughout the ages.
In the modern era, the Dweller influenced Zoltan Drago to develop the gas and costume of Mister Fear. The Dweller also manipulated a number of people into killing themselves in exchange for promises of eternal life, transforming them into Shade-Thralls, who nearly overwhelmed Thor and Hercules before the Dweller withdrew to avoid detection. While using other Shade-Thralls against Dr. Strange and Clea, the Dweller gained sufficient power to break Zhered-Na's spell. Still acting from the shadows, the Dweller empowered Barbara Robb as the reality-altering Dream Weaver, who sought to steal the Book of the Vishanti before Strange revealed the forces with which she was dealing and erased her memory and powers; then secretly aided the demons Ludi and Ningal against Strange. Though his agents met defeat, Strange was unable to determine who had sent them, and the Dweller claimed victory by introducing doubt and fear into the one being who could oppose him.
The Dweller later joined with the other Fear Lords (Kkallakku, hatchlord of the Fear-Eaters; the enigmatic Lurking Unknown; the Olympian goddess Nox; Nightmare; Straw Man; and the lesser D'spayre), plotting to have them magnify humanity's fear, then let Strange defeat them; the Dweller would feed on this fear and become supreme Fear Lord. When the Dweller and Nightmare contended to prove their mastery of fear by plaguing humanity in waking and sleeping hours, respectively, they went too far, and pushed humanity into despair. The virtually all-powerful D'Spayre then attacked his former masters and the Dweller abandoned his android body as it was destroyed, fleeing through a dimensional aperture. Having met defeat in direct conflict, the Dweller continues to plot from the shadows.