Ferdiad is a character from Final Fantasy XIV. Originally serving as the final boss of the dungeon Amdapor Keep (Hard), he later appears in Final Fantasy XIV: Heavensward as a antagonist during the Shadow of Mhach storyline.
Ferdiad is a powerful Voidsent who has the appearance of a demonic jester. He has horns and other protrusions that resemble the outfit traditional worn by harlequins, and carries a large, scythe-like staff.
When the Adventurer purged Amdapor Keep of the violent cultists, the Lambs of Dalamud, they inadvertently completed a ritual that the group had prepared. The cultists' spilled blood was the final ingredient needed to summon a host of powerful Voidsent, led by Ferdiad. The Adventurer is sent back to the Keep in order to deal with this new threat, eventually facing Ferdiad in battle. Although they defeat and seemingly destroy him, after they leave, Ferdiad's laughter is heard echoing through the halls, implying that he survived the encounter.
During the Shadow of Mhach storyline, the Adventurer travels to The Weeping City of Mhach alongside Leofard and Cait Sith, in search of a powerful artifact capable of easily defeating Voidsent, known as the Nullstone. After they defeat the enemies that bar their path and obtain the Nullstone, they are suddenly confronted by Ferdiad, who has Radlia as a hostage. Recognizing the Adventurer from their earlier encounter, Ferdiad offers thanks to Diabolos for giving him the chance for revenge, and demands the Nullstone in exchange for Radlia's life. Leofard manages to use a bluff to convince Ferdiad that he doesn't care about Radlia, and goads the Voidsent into attacking him, leaving him open for Cait Sith to use the Nullstone against him. Though injured by the Nullstone's power, he manages to flee.
Ferdiad is later seen meeting with Diabolos above the city. He reports his failure to Diabolos, apologizing and promising to redeem himself by destroying the Adventurer the next time they meet. The two Voidsent then depart the city.
Ferdiad was a figure from Irish Mythology. He was a friend and rival of Cuchulainn and a fellow pupil of the warrior woman Scáthach. This is reflected in the Shadow of Mhach storyline, as Cúchulainn appears as a fellow Voidsent boss during the quest, and Ferdiad works to free the game's version of Scáthach.