Powers: Exists in an interdimensional realm where he can observe events on Earth without himself being seen. He can will himself to shift into the Earth dimension, becoming visible and intangible or both visible and tangible. He could cover more distances on Earth via the other dimension.
Death-Stalker also had a "cybernetic death-grip" device which he wore as gloves and which he activated by mental command. The device emitted microwaves which instantaneously caused whomever he gripped to die. He had to fully materialize within the Earth dimension for the death-grip to be effective.
Weaknesses: Death-Stalker could not remain in the Earth dimension for more than several hours at a time.