Ultraman X Darkness is a dark counterpart of Ultraman X appearing in Ultra Galaxy Fight. He is a villainous, corrupted version of the heroic Ultraman X, created or empowered through dark forces to serve as an enemy to the Ultras. In the series, he functions as a dangerous combatant and an embodiment of twisted Ultraman power, confronting the protagonists in battle and highlighting the threat posed by darkness overtaking heroic strength.