recursion is like patterns for example it's like mana having multiple forms or elements in magic or undead being immortal even though they are different in terms of properties but its not just bound by core mechanics you can also add recursion of behavior in multiple NPCs of same town or a village and this example can also fit easily with the theme of folklore because lore can easily change the behavior of the residents but these are just some examples i came up with after reading the meaning of the word recursion in the internet i hope it helps.
and if you want easy ways to implement recursion the one of the simplest concept would be simple game mechanics that uses other parts or mechanics of the game .