Before the Shattering eliminated magic, many beings from other planes roamed free on Ezeth. Elemental spirits roamed the deepest jungles of Imea and skated across the plains of Cadrin. Beings of pure water and energy relished in the plentiful magic that once was, drifting between their world and our own. The Shattering brutally ripped what beings had remained from their homes, from their lives, forcing them into mortal bodies to live amongst the scattered cities that remained. These beings were never truly from here, and thus never feel at home, constantly drifting, yearning for the lives that were ripped away from them. Many were captured and forced into slavery, with crueler beings trying to extract magic from them in any way they could.
Some attempted to make a quiet home for themselves, finding a mate, and occasionally, to their surprise, siring children. These children appeared to be human, though something always seems to be imperceptibly off. The elemental parent rarely stuck around, never being able to truly fit into society acceptably, and many of these children remain unaware of their own heritage to this day.
Through investigations from the party, it would seem that magic acts as a trigger for half-elementals to take on the appearance of their otherworldly parent, if only for a short time.