Ziekfried is a Metal Demon, a race of beings intent on claiming Filgaia
as their new homeland. His goal is to revive Mother, the incapacitated leader of the demons. Her inactive body is successfully reclaimed by the Quarter Knights prior to the game's events (depicted in a cut-scene that can be viewed by leaving the game at the title screen for a few moments), and the first half of the game sees Ziekfried trying to reclaim the three parts of Mother's heart.
He is successful in acquiring the entire heart and reviving Mother, but is shocked to find they have very different plans for Filgaia. Ziekfried wants to enslave humanity and create a new home world, but Mother's desire is to destroy the planet and everything on it (including herself and the rest of the Metal Demons). When the protagonists - Rudy Roughnight, Cecilia Adlehyde, and Jack Van Burace - infiltrate the Photosphere, the Quarter Knights base, he tricks the group into defeating a weakened Mother and buries her at the bottom of the ocean, beneath the Photosphere ruins.
With Mother seemingly defeated and Ziekfried once again commanding the Quarter Knights, he attempts to destroy the Ray Line, a planet-wide network created by the Guardians as a last resort to pool their strength together against threats. The protagonists battle Ziekfried, and the encounter opens up a dimensional rift that drags him in. Waking up in the ruins of the Photosphere, Mother is still alive and consumes him. This fusion of Mother and Ziekfried is known as Motherfried and is defeated by the party at Malduke, the space station that has the destructive power to destroy Filgaia. As the party teleport back from Malduke to Filgaia, a weakened Ziekfried interrupts them and forces one last battle, which again ends in defeat for him.