The X-Men have been drawn into all types of conflicts over the years and have sometimes faced supernatural threats. This is one area in which the devout and noble-hearted Nightcrawler has always been important to the structure of the team. It turns out he may be even more significant than anyone really realizes, as evidenced by his handling of an incredibly powerful demonic force.
In Nightcrawler #12 (by Roberto Aguirre-Sacasa, Darick Robertson, Rodney Ramos, Matt Milla, and Rus Wooton), the veteran X-Man was offered a deal by Mephisto that was very similar to others offered by the devil. However, the blue-furred mutant responded in a way unique to the heroes of the Marvel Universe. Not only did he refuse the offer but he literally punched the devil in the face.
Recent events in Amazing Spider-Man revealed that Mephisto has been manipulating events behind the scenes for decades. Due to a vision of Peter Parker's future spider-powered daughter May proving to be the hero to upend his potential take over of the world, Marvel's devil dedicated himself to bringing down her father and ruining his life, all in the name of gaining an edge in the eventual conflict. This is what spurred him to offer a deal to Norman Osborn, and what eventually led him to offer a bargain to Spider-Man himself in a bid to break up him and Mary-Jane once and for all. But across the history of the Marvel Universe, there's another notable hero that Mephisto has tried to convince to give up his place in that battle: Nightcrawler.
In Nightcrawler #12, after surviving a harrowing series of supernatural battles, Kurt Wagner is on the mend and dealing with his own internal doubts. After confronting and defeating the demonic being known as the Hive, the mutant hero learned that he had encountered the being earlier in his life without realizing it. Years before he joined the X-Men, the Hive had possessed his adopted brother Stephan Szardos. Driving him to madness, Stephan tried to murder numerous innocents and, left with no other choice, Kurt took his life in the ensuing scuffle. This guilt had long haunted Kurt, and even defeating the demon responsible did little to soothe his soul.
On his birthday, Nightcrawler was confronted by Hive's "distant cousin," Mephisto. The demon revealed he hadn't come seeking a fight. Instead, he wanted to offer Nightcrawler a bargain: in the coming wars that will determine if Mephisto is victorious in his conquest of the world, it turns out that Nightcrawler has an important role to play. But Mephisto doesn't want him in that battle, while the "forces of good" have quietly been positioning Nightcrawler to do so. In exchange for not taking part in the conflict -- becoming a "conscious objector" -- Mephisto offers to resurrect Stephan with his mind and soul restored to how they were before the Hive's interference. Mephisto doesn't even finish speaking before Nightcrawler punches him in the face for even suggesting the deal.
The very notion offends the devout Nightcrawler on multiple levels, and he vows to bring war to Mephstio when the day comes. Mephisto departs, infuriated, and Nightcrawler is returned to his birthday party at the Xavier Mansion. It's an especially impressive moment of resolve coming from Nightcrawler, suggesting he's more uncompromisingly heroic than even someone like Spider-Man. It's also an early and interesting tease of the war that Amazing Spider-Man has now confirmed is eventually coming. It appears that like Spider-Woman, Nightcrawler -- or potentially even a variant version of his alternate reality daughter with the Scarlet Witch, Nocturne -- has a role to play in the war to come. And unlike a certain wall-crawler, Nightcrawler has always firmly known which side he's on.