WARNING: The following contains spoilers for The Eternals #6 from Marvel Comics, on sale now.
When facing off with Thanos, the other heroes and villains of the Marvel Universe have been forced to pull out all the stops. Otherwise, they risk the Mad Titan overwhelming them and destroying any chance they would have to overcome his might. Occasionally they've even needed to steal ideas from his own plans to use against him.
While combating an unleashed Thanos in The Eternals #6 by Kieron Gillen, Esad Ribić, Matthew Wilson and VC's Clayton Cowles, Sersi deployed a devastating attack against Thanos that was actually inspired by one of his most brutal murders ever.
During The Eternals #6, Sersi and many of her fellow Eternals end up in a battle with Thanos. Together, they're able to use their powers to contend with the Mad Titan. But there's little they can do to fully stop him -- until Sersi reveals she's been sitting on a powerful attack. It turns out that Jennifer told her fellow former Avenger She-Hulk about her brief demise at the hands of Thanos in Infinity Gauntlet by Jim Starlin, George Pérez and Ron Lim. She-Hulk was part of the final offensive of heroes who attacked Thanos during that event, trying to stop him from using the universe-altering Infinity Gauntlet any further. Every hero present was killed in the fight, including She-Hulk -- who, standing beside Namor, was covered in a fungus that quickly spread across their bodies and suffocated them.
Despite the universe being promptly reset following the conflict, She-Hulk apparently retained some memory of her demise and shared the details with Sersi, which haunted the Eternal. Sersi apparently had trouble sleeping for days after learning of this story -- but was also inspired by the story to develop a secret technique that she utilizes against Thanos. A master matter manipulator like Sersi was able to take the idea and expand on it, creating a fungal plasma replicate that spreads across the body of someone covered in it -- and setting off pyrokinetic poisons that leave the target in intense pain as they are covered in the spores.
She unleashes it against Thanos, catching him by surprise as it quickly spreads across his body and forcing him to his knees. Notably, it's this attack that fully turns the tide of the battle. Before Sersi deployed it against Thanos, they were barely able to slow him down. But this fungus is quick to spread and slow him down, allowing the other Eternals to continue their attacks and actually win. It's also just very fitting -- and rewarding -- to see someone like Thanos, who indulges in terrifying and terrible tortures on others, have one of his most brutal methods of murder turned against him.
Although this likely won't stop Thanos forever, it's still one the best attacks someone could deploy against the Mad Titan. Gods have gone up against Thanos and had difficultly bringing him down. It just took someone as powerful, creative and unrestrained as Sersi to fully utilize it to the best of its ability.