Secret Food can be categorized into three types. First is the Evolutionary Secret Food, which extracts the essence from all manner of materials and allows the beast to evolve. For example, the Void Saintess Fruit, which transformed Little Spider, is an unparalleled marvel.
The second type is the Sacrificial Secret Food, which harnesses taboo times and ancient entities from historical worships. However, due to its high-level nature, it's temporarily unavailable for use.
The third type is the Skill Secret Food, which can be made by refining special extraordinary materials. It's essentially an edible version of the Skill Learning Machine.
Unlike the usual way of learning new skills for beasts, Skill Secret Food doesn't require matching of attributes or races. One can acquire the skill simply by eating it, with beginner-level proficiency as a bonus.
While forced learning is possible, if the attribute gap is too wide, it will be extraordinarily difficult to improve proficiency later.