Sterling actually found himself trapped between two dimensions, able to return to Earth at will but only for a few hours at a time; furthermore, the mutation caused his skin to become chalk-white. He stole a pair of gloves from AIM that gave him a "death-grip," and began calling himself the Death-Stalker. He tried several times to kill Daredevil and build a new t-ray machine, but was each time beaten by Daredevil.
He allied with Gladiator against Daredevil. Death-Stalker traveled to the Florida Everglades in search of papers relating to Ted Sallis's experiments, and encountered the Man-Thing. He stole a set of ancient Lemurian crystal lenses from the Museum of Modern Art, and battled Daredevil. He masqueraded as Death's-Head (Karen Page's father), and battled Daredevil and the Ghost Rider. Death-Stalker next assembled a large gathering of criminals to take part in an undisclosed plan, and battled Daredevil yet again. He stole a scientific apparatus from Stark International.
Finally, Death-Stalker plotted his ultimate destruction of Daredevil. He attempted to kill Daredevil while the crime-fighter was hospitalized. He battled the Avengers. He created a new Unholy Three as a new group of Ani-Men and had them kidnap Matt Murdock, whose secret identity as Daredevil he had learned by observation from between dimensions. Daredevil was taken to St. Stephens Cemetery, and there Death-Stalker killed the Ani-Men and attacked Daredevil. He materialized from his other dimension while in mid-leap through a gravestone; the trauma killed him instantly.
His "cybernetic death-grip" device, stolen from AIM, was worn in his gloves, which emitted a dose of microwave radiation when activated by mental command, killing any living creature in contact with it. Death-Stalker had to fully materialize on Earth for the device to be effective. This energy has been described as microwaves, but seems to have properties of both lightning and truly intense cold.
Philip Wallace Sterling was a brilliant criminal mastermind, in addition to being an accomplished inventor and scientist with extensive knowledge of advance scientific apparatus.