Doctor Strange: The Oath #1 (2006)

On a rainy night, Iron Fist and Araña are waiting in a special private clinic that treats superheroes. Suddenly, Wong crashes through the doors carrying the bleeding and unconscious body of Doctor Stephen Strange. He's been shot. The Night Nurse (technically Night General Practitioner, but the codename is catchier) helps Wong carry him to an operating room, where Strange's astral form appears to her.

The man who shot Strange, known as Brigand, meets his employer in the penthouse suite of an office building and announces that Strange is dead. In his possession is the bottle of green liquid he was hired to steal. The other man knows enough of Strange and magic to be shocked at this news, but Brigand shows him Adolf Hitler's personal weapon, loaded with silver bullets; enough bad karma to get through Strange's magical defenses. Brigand's employer shrugs this off and takes possession of the bottle, commenting that he's going to study it -- and probably pour it down the drain.

Guiding the Nurse through his own surgery, Strange explains that the green potion is an elixir he had retrieved from another dimension. His original intention had been to find a cure for his manservant Wong, who has developed an inoperable brain tumor. The potion he found, Otkid's Elixir, was rumored to "erase what troubles the mind of man," but when he sent a sample of it to be tested, he discovered that what he had found was actually the cure for cancer.