Hafgan, a figure in Welsh mythology, is depicted as one of the kings of Annwn, the otherworldly realm. In the First Branch of the Mabinogi, he emerges as the primary adversary to Arawn, another ruler of Annwn. Their domains lie adjacent, and Hafgan perpetually engages in warfare against Arawn.

In the tale of Pwyll, Prince of Dyfed, Pwyll strikes a bargain with Arawn to exchange places for a year and a day, agreeing to combat Hafgan on Arawn’s behalf to resolve his ongoing conflict. Arawn instructs Pwyll to deliver a fatal blow with a single stroke should he confront Hafgan, recalling a previous encounter where Arawn had inadvertently spared Hafgan by granting him an additional strike.

Assuming Arawn’s guise, Pwyll engages in battle and severely wounds Hafgan, shattering his shield and armor and felling him to the ground. As forewarned, Hafgan implores Pwyll to deliver the finishing blow, but Pwyll refuses, stating, “I may yet repent this, but, whoever else may slay you now, I will not do so.” With his impending demise apparent, Hafgan concedes defeat and relinquishes his leadership. Witnessing their lord’s defeat, Hafgan’s followers acknowledge Arawn as the sole ruler of Annwn, submitting to his authority.