The Dagda was born in the dimension of Otherworld and became ruler of one of the four cities inhabited by the Tuatha de Danaan. Thousands of years ago he was among the Tuatha who traveled to Earth under the command of his older brother Nuada. He served as the latter's second-in-command. Nuada
was deemed unfit to led after the loss of his hand in battle with the Formarians, another race from Otherworld he came to Ireland first.. He was replaced by the half-Tuatha Bres, but after seven years Bres was driven out for being a tyrant. The Dagda succeeded him as king.
One of the Dagda's more controversial decisions was to return to Otherworld around 350 AD in advance of a new race coming to Ireland. He was opposed by his own son Bodb Derg the war-god, but emerged victorious in the power struggle and banished his son. At some point the Celtic gods entered a Cold War with the Asgardian gods due to treatment at the hands of their mortal worshipers by the Vikings.
In modern times, the Dagda was convinced by his younger brother Leir
to end hostilities with Asgard and aid them against the serpent god Seth
. The Dagda used his magical abilities to send Leir and his warriors to Asgard while he stayed behind to oversee the battle. He later joined it himself. After Seth's defeat, the Dagda prevented a renewing of hostilities with the Formarians by separating the two sides with a swarm of summoned bees. He was tricked into opening a portal to Asgard for Leir and attempted to stop him from venturing there upon learning of his intentions to woo Sif
. Leir jumped through the portal before it could be closed.
The Dagda is one of the most skilled practitioners of magic among the Tuatha de Danaan. This combined with his own natural mystical abilities make him one of if not the most powerful Celtic god. His abilities include the opening of portals between dimensions that can send entire armies to cross and summoning swarms of insects that are capable of annoying even gods.
It is unknown how his magical powers compare to other skyfathers like Odin
He possesses several magical articfacts. He has the caldron Undra that has endless physical and spiritual nourishment. He has a magical harp that can control the weather. He has a wooden club that is either a powerful striking weapon that can kill at least nine normal men with one blow, heal them or act as a channel for is godly powers.