Doctor Nikolaus List was a high-ranking scientist within SHIELD and the head of Echidna Capital Management, until he became dissatisfied with the organization and was recruited by Baron Strucker into his branch of HYDRA. List then went on to assist Strucker in his experiments revolving around Alien-Enhancement, with projects such as hunting Inhumans, and most notably using the cosmic energy of the Chitauri Scepter on test subjects to observe its effects on certain humans. This series of experiments would end when both SHIELD and the Avengers would bring down Strucker's branch of HYDRA. In order to preserve HYDRA's secrets, Strucker ordered Nikolaus to delete all the sensitive information, but before he could delete any of it, Iron Man blasted List with a repulsor beam and left him unconscious but severely wounded while he recovered the necessary tech to ultimately bring about the rise of Ultron.
Following the battle's conclusion, List was immediately sent to NATO's medical center. After several months in recovery, during this time of which even the low-ranking thug Kebo thought he followed Strucker in death, List was offered various deals of which he could be placed in witness protection. Nikolaus refused and was placed in prison, but still having needed occasional medical assistance. His loyalty proved vital, as a HYDRA team led by Taskmaster broke into the prison and removed a large portion of the population including List. He was sent to Arnim Zola for medical treatment, after which he would be truly healed from his wounds from the Battle of Sokovia. Afterwards, List was tasked by HYDRA to continue his work with cosmic research, as even though their god Hive turned out to be a traitor focusing only on himself and his Inhuman-supremacy goals, there were other "gods" that could prove more than enough to cover the devastating loss caused by Hive bringing down most of the organization's front leaders with him.