Nathan Garrett was a turncoat S.H.I.E.L.D. agent who joined HYDRA. The son of Sarah and David Garrett, he was the twin brother of Jonathan Garrett. When he was injured and presumed killed during a mission in Sarajevo, he survived by becoming the first Deathlok soldier. In order to make S.H.I.E.L.D. pay, he joined HYDRA by kidnapping and imprisoning his twin brother John under Wolfgang von Strucker and Nikolaus Geist's orders, take his name, and used his Level 7 Clearance to become the Clairvoyant, the mastermind behind the Centipede Project.
While keeping his old name a secret and used his brother's identity to make everyone S.H.I.E.L.D. believe that was John for real, he recruited Grant Ward into HYDRA and became a fatherly figure to him. Just as the uprising of HYDRA began, Nathan broke his cover, fled S.H.I.E.L.D. and restarted the Centipede Project with the goal to recreate the life-saving drug of GH.325, which he desperately needed to heal his failing organs. He then attempted to use the knowledge given to him by the drug to take over the world, but was stopped by Phil Coulson, Deathlok, and Nick Fury in the Battle at Cybertek, and was subsequently killed by the Peruvian 0-8-4 while he was upgrading himself.