And in which mythology were there elementals?
I only know of them in Slavic myths - leshy, devils in a whirlpool.

They weren't in mythology. It was just a kind of superstition. They represented the elements as living beings. Because ancient people probably thought that anything that moved was alive. For example, water flows, so it's alive. By the way, scientists now believe that it is alive. Because when freezing, it freezes differently depending on the music. With some symphonies, it freezes into a beautiful pattern. With rock music, it freezes into a scary blot. Or, for example, fire spreads, so it's alive, the wind blows, so it's also alive, and so on.