WARNING: The following contains spoilers for Season 5 of The Seven Deadly Sins, now streaming on Netflix.
Much like his captain, The Seven Deadly Sins' fox sin, Ban, has always been motivated by the desire to save the woman he loves. The tragic fate of his lover Elaine has been his constant motivator since his debut in the anime's first season. After being partially revived, thanks to the abilities of the Ten Commandments' Melascula, Elaine finally entered the main story. However, due to this being only temporary, Ban has devoted himself to bringing her back to life permanently, as he cannot join her in the afterlife due to his immortality. Thanks to his time in Purgatory, Ban may have discovered a way to revive Elaine for good.
Season 5, Episode 8, "The Doorway to Hope," finds Meliodas, Wild and Ban locked into their decades-long battle against the Demon King. While attacking their opponent, Ban finds an opening to use his Physical Hunt ability to siphon away the dark god's power. However, instead of receiving the Demon King's power, Ban feels his own energy being drained away.
Meliodas reveals that this is an effect of the Demon King's ability, "The Ruler," which inverts every attack used against him. After the trio's 6,093rd defeat, they take time to regroup and reflect on the impossible task before them. As the warriors prepare to face off against their adversary once again, Ban uses his life energy to heal one of Wild's wounds, explaining that he had learned this technique after experiencing the effects of the Demon King's ability. This new ability gives Meliodas an idea.
The trio once again battles the Demon King, but as the Demon King activates his power, he suddenly becomes weak, falling to the ground. This is due to Ban using his newfound ability to give the Demon King his life force. When The Ruler is activated, this "gift" is inverted, causing the Demon King to lose power. Despite gaining the upper hand, the Demon King is able to adjust and quickly recovers. However, Wild stays behind to hold him off, allowing Ban and Meliodas to escape.
Having escaped through the portal to the real world, Ban appears before the rest of the Sins. He explains to them that the captain is returning, and they all need to help him. However, he walks off in the opposite direction, saying that he'll join them, but first has something he must do.
The scene shifts to the Holy Knights of Leonis and a cadre of Fairies fending off a horde of demons. There, Elaine is engaged in battle. Despite their efforts, the group is quickly overwhelmed and Elaine resolves to save the others by sacrificing her remaining life energy, provided by Melascula's spell, to attack the demons. As she completes her spell, her wings disintegrate, and she plummets from the sky.
As she falls, her thoughts turn to Ban, who suddenly appears and quickly defeats the horde. Before her body can hit the ground, Ban catches Elaine, who thinks she's dreaming. Happy she could see him one last time, Elaine fully accepts her death. As her body goes limp, Ban assures her this is not the last time the two will see each other and uses his new ability, now named "Gift," to give Elaine his life energy, reviving her completely. At long last, Ban is able to fulfill his deepest desire, albeit at a cost. Due to the incredible amount of energy it takes to revive the dead fully, Ban's immortality is now lost.
This is a massive blow to Ban's abilities, as he is often horrifically mutilated in battle, sustaining wounds that would kill anyone but an immortal. This comes at quite the worst time, as the final battle against the Demon King in the real world quickly approaches. With his immortality lost, Ban might not stand a chance when the Sins need him most.
