Fallen is a trait for the Neutral class exclusive to the Shadowverse Flame anime series.
Cards with this trait are dark versions of angelic followers, transformed by cards like Winged Inversion and Fallen Shot.
Their playstyle revolves around switching from the original form to the Fallen Angel form and vice-versa in order to make use of the Fallen form's new abilities and the buffs they gain when switching back, and also exploit the abilities of cards like Harbinger of the Night and Angel of Chaos.