Gallagher is the main villain and final boss from Valis IV.
Gallagher was the son of Asfal, a king from the Dark World. Hoping to succeed his father's throne and, Gallagher started growing powerthirsty because of the Red Ring, the emblem of the throne, using it's power to dominate everything, but his father opposed to him, so Gallagher banished him from the Dark World. Upon learning of what happened, the gods imprisoned Gallagher and his followers inside a large crystal, which was sank beneath the ocean in the Human World.
Centuries later, the crystal emerges from the ocean, freeing Gallagher and his men. He once again puts his plans into motion, terrorizing the Human World and the Dream World. He kidnaps Valna, current queen of the Dream World, intending to sacrifice her to increase the powers from the Red Ring. Lena, a member of the resistance against Gallagher's regime, decides to go rescue Valna along with her sister Anu, but Cham, who leads the resistance, is against the idea, until she hears Yuko's voice, who tell her to let Lena go. Lena and Amu go after Valna while Cham stays behind protecting the people.
Lena and Amu find Valna, but Gallagher shows up and stops them, but before he can kill them, the two are teleported away by Asfal. Asfal tells them that the only thing capable of defeating his son is the Valis Sword, so he leads them to Heaven, where the sword was guarded by Yuko. Upon reaching Heaven, Lena meets with Yuko, who tests her to see if she's willing to become the new Valis Warrior. Lena passes the test and is bestowed with the Valis Sword, so the group travel back to the Human World and confront Gallagher's generals.
After the generals are defeated, they find Gallagher about to kill Valna. As Gallagher throws his axe on Valna, Amu steps in and takes the blow, dying afterwards. Lena and Asfal then follow Gallagher, confronting him on his lair, the Red Moon. Asfal fights his son and is defeated, so Lena steps in and fights him, defeating him. Upon being defeated, Gallagher apologizes to his father and dies on his arms.