Umbral Wave is a skill that appears exclusively in Dragon Quest: The Adventure of Dai: A Hero's Bonds. It sends out bursts of dark energy from the user's spear that makes enemies more vulnerable.
Umbral Wave appears as a skill for Larhart and the Luminary Leader as a Hero if they are wielding a spear. It is a mid-range attack that inflicts physical Shadow damage three times over a small area and lowers the target's Shadow Resistance temporarily when using a counterattack. The main way to unlock the skill is by playing during Larhart's A Loyal Land Rider's Pledge event or from the Shop Exchange.