Dagda is the supreme god in Celtic mythology. His name means "the good god", good as in good at everything, as opposed to morally good. He is portrayed as being armed with a magical club. During the battle against the Irish aboriginal, Fomorians, Dagda is injured and begins to live a reclusive life. His positions are succeeded by his brother Nuada and daughter Brigid.
A demon who meets Nanashi in the underworld. He informs Nanashi that he is currently in Yomotsu-Hirasaka, and states that he has died, and that his friend, Asahi, would soon follow him. Dagda claims that Nanashi has accomplished nothing in his short life, but that together they (Dagda and Nanashi) could change that. Dagda says that he will revive Nanashi, if he agrees to work with him. Nanashi agrees, and Dagda revives him, leaving behind green markings on his left hand, and Nanashi's eyes turn green. Dagda states that he is now his personal Godslayer, and will commit "deicide" as his puppet, though he later says that Nanashi doesn't necessarily have to be obedient to him. After resurrecting the young cadet, Dagda enters his smartphone to observe him during his battle against Adramelech, repairing the smartphone to allow him to summon and recruit demons to his aid.
Through out the course of Nanashi's journey, the player learns that Dagda's ultimate goal is to kill all Gods and Demons, believing that divine power had corrupted them, and he would be no exception. To that end, he needed a pawn, that being Nanashi, who could destroy them, as a Godslayer has the power to kill not only deities, but also their worshipers, as they only exist because of the faith their followers provide for them.
In the Anarchy Ending, Dagda succeeds in his plans, as Nanashi has slain YHVH at long last, albeit at the lives of his friends, and many others. Regardless, he is capable of replacing YHVH, though he passes this ideal to Nanashi, who is human, thus he can always remember the consequences of being corrupted and becoming arrogant. He later disappears after the creation of the New World Nanashi establishes.
He is voiced by Shūichi Ikeda in Japanese and Xander Mobus in English.
Dagda is a dark element unit obtained through a twitter event leading up to the Shin Megami Tensei IV Final x Brave Frontier event. He was released to all players after surpassing the goal of 4000 tweets.