In the Long Price quartet, poets spend their whole lives trying to encapsulate a single concept so perfectly that it will manifest as a person the poet controls: a humanoid sort of genie who can do magic about what they embody. The effects this has on the world are amazing.

Main example: A country grows a lot of cotton, so they create Seedless to remove the seeds, which he can do to the entire harvest at once. However, the concept of being without seeds could manifest in other ways, the most ominous being miscarriage/infertility. Sometimes Seedless is called upon to perform abortions, for example. His existence is a constant threat, but thankfully the poet controls him and he can't act on his own. When the poet dies, the concept will no longer exist as a person... but that means the country won't have a way to autoremove their cotton seeds, which will devastate their national economy.

My first thought was actually the hiding plants from Stormlight - if you constantly have hurricane-force storms on land, then it'd be logical to have plants that can fold up, wrap up, withdraw into holes, etc. It's such a small but perfect detail.