I had this idea before, but what if DF's are made by extracting the "essence"/"soul" of a creature or object, modifying it, and then infusing into a fruit. Once the fruit has been eaten, the essence that lies within the fruit becomes tethered to the creature/object, in turn granting them the characteristics (abilities) of the essence until they're complete death/destruction which severes the tether and the essence flies off to find a fruit.
Which then leads into the potential
reason why the Yami Yami no Mi is so special. Maybe with it's infinite pull, it's capable of temporarily severing the bond between fruit and user by pulling in the essence. And maybe it's possible that if the target dies and the bond they have with the fruit ceases to exist, the Yami Yami might be capable of permanently pulling in the essence, which could possibly allow the user to use the pulled in essence through the Yami Yami no Mi.
Zoans are unique in that while they also have an essence like Logia's and Paramecia's, a Zoan has a unique trait, a Consciousnesses/Will. So while a user may have control over a Zoan, the Zoan has a subtle influence over the user (like Lucci's bloodlust might come from his carnivorous Zoan fruit). And a Zoan awakening makes the connection between a user and their fruit so close, that if the user doesn't have a great will, they can be controlled by the Zoan within. And as seen with objects, if you give an object a Zoan, the Zoan flat out becomes the dominant force since there is no Will to oppose it.
This is just what I think, so don't take it seriously.
As for why Nika is the Sun God, well it's possible that whenever he freed the one's in chains, the joy and laughter he brought to his followers probably shined as bright as the Sun. And if Nika was anything like Luffy, people naturally gravitated towards him because of his charm and personality and the way he brought joy to all, similar to how the planets gravitate towards the sun. Some religions and beliefs believe that the Sun is the center of the universe, like how Nika likely was the center of attention wherever he went. And it's also possible that some of the fire stuff Luffy does (like Red Hawk, Red Roc, and the fire run) might come from his fruit. Who knows lol.
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Why that there
