From publisher blurb:
The roaring of never-ending flames, the crashing of titanic waves, the howling of raging typhoons, the rumbling of moving earth, all of these are sounds familiar to mephits. But while their primordial cousins command the purest aspects of nature, these small imp-like creatures are little bits of elemental runoff fused together and given the breath of life.
Expanding upon the character-building mechanics of 5E, this PDF allows you to create playable mephit characters, paraelementals with a unique perspective as interplanar invaders, former mages' familiars, and sociable pack creatures.