It's been awhile since we've seen Wolverine starring in a movie. The last time fans saw Hugh Jackman's mutant hero for more than a few seconds was in 2014's X-Men: Days of Future Past. When we left him, Wolverine had fixed the future, saved the X-Men, and was happily living at the X Mansion in Westchester. Now years later in Logan, Wolverine is getting old, the X-Men are dead, and he spends his waking hours so drunk he can barely throw a punch. Over the course of the film — spoiler alert — he injects himself with a mysterious green compound to accelerate his healing powers and give him a boost of energy. But what is this green stuff in Logan? And what does it mean for Wolverine?
The green stuff in Logan is a serum that emphasizes the Wolverine's powers. In the film, Wolverine is slowly dying from what he believes to be Adamantium poisoning. As a result, his speed, strength, and healing powers are not what they used to be. But, when he is injected with a small dose of the green serum, his healing powers kick back up, and his strength is temporarily restored. That said, the green serum is not actually made for him. It's specifically tailored to X-23 (aka Laura) and X-24, both Wolverine clones. In fact, Wolverine finds the serum in Laura's belongings.
The serum is first seen used on X-24, the vicious Wolverine clone created by Dr. Zander Rice, the son of the Doctor who worked at Project X when Wolverine was there. Rice is seen injecting X-24 with the serum after a grueling battle, and tells him that it will help him heal. Later on in the film, Wolverine is given some to help him heal too, but he is warned not to take too much at once. The entire bottle could kill him.
The exact name of the serum is not stressed in the movie, and it doesn't appear to have a comic book counterpart. In the film, it was created by Alkili Transigen, Essex Corp's successor, if you will, and the group that created Laura. While it appears safe to use for the mutants Transigen created, like Laura and X-24, high doses are known to be fatal. It's unclear whether the green serum is only effective on Wolverine's DNA, or if any mutant who injected themselves with it would experience a boost in powers.
The green stuff in Logan is Wolverine's secret weapon, but it's also his biggest threat. And I have no doubt that it will spark theories as to how the green serum might impact Wolverine's future.