Chapter Text
Shanks remembers being more than what he is now, he dreams of a past he shouldn’t know and sees more than he has any right to. He doesn’t know what his old name was or what he used to be but he knows what he has to do. He knows that he used to have something to do with Fate and that he has to set a Prophecy into motion but for now he is content to just be Shanks, to be a pirate and enjoy freedom in a way he knows he couldn’t before. He takes up drinking to dull the whispers of Fate, to block out the future in order to enjoy the present for once.
Before landing on Dawn, Shanks never wanted kids but he grew to see Luffy as his own. He vowed to himself that he would stay Shanks for as long as Luffy was there to anchor him to his humanity. No matter how much his old name called to him, Shanks wouldn’t answer, wouldn’t take up his old mantle until his kid stopped needing him to be human.
All of Shanks' carefully laid plans disappeared when Luffy ate the devil fruit. He originally planned on taking his son with him after passing the fruit to the rightful owner but that was no longer possible. By eating the devil fruit Luffy stole a fate that wasn’t meant for him and the world would be trying to fix this mistake by getting the fruit to the rightful owner. Once a devil fruit has been eaten the only way to get it back was to kill the user, allowing it to regrow somewhere else in the world.
Shanks did the only thing that he could think of to save his son, he allowed the sea king to eat his arm and left Luffy behind with a promise to grow stronger. He weakened himself so Fate couldn’t set things right, he made sure the world wouldn’t have the power to arrange Luffy’s death. Shanks left his son behind so he could draw the world's attention elsewhere, allowing him to grow in relative peace. He made Luffy promise to grow stronger than him so Fate would never be able to take back the power that Luffy stole.
When asked Shanks will say that he lost his arm in a bet because as far as he was concerned he did. He bet his arm on Luffy. That his anchor will survive everything the world throws at him, that his son will grow strong enough to bring change, that having Luffy around will be better than allowing him to die to start the prophecy that would save the world from Imu. Shanks knows that he bet more than just his arm but he doesn’t care, pirates are selfish and Luffy was his. He would allow the world to burn to keep his people safe and for Luffy, Shanks would set the world on fire himself.
Others that are like him or know who Shanks used to be are horrified because they know what Shanks really bet on. They know that he didn’t just bet his arm but the world as a whole, they know that Shanks has set the world down a path it wasn’t supposed to go down and no one can fix it because that was supposed to be his job. They see Shanks actions as him going rouge and wonder with dread how many would follow his footsteps. Gods were selfish creatures, who's to say others wouldn’t put their wants above the needs of the world.