Luffy ate the Hito Hito no Mi, Model: Nika, which is a Mythical Zoan type Devil Fruit. This fruit allows him to transform into the legendary Sun God Nika and has been a key factor in his ability to defeat powerful foes like Kaido. The Hito Hito no Mi, Model: Nika, is a unique fruit that combines Paramecia and Zoan powers, enabling Luffy to alter his body and surroundings based on his imagination, and it has been sought after by the World Government for centuries due to its immense power and connection to freedom