The Zombie Dragon is the reanimated corpse of Gaelion, Wyndia's adoptive father. After Ren slayed the "dragon causing problems" on the mountain near East Village, Gaelion's body started decomposing leaving the land horrendously polluted and because he was a fragment of that Dragon Emperor his core's magical power reorganized into the flesh of the Zombie Dragon. During the fight Naofumi's dear companion, Filo, gets eaten and Naofumi believes she has died. He is over taken by anger and his lack of strength giving into the Wrath Series's temptation for power. Using it's strength he is able to counter the Zombie Dragon's attacks dealing incredible damage with each counterstrike but slowly losing his ability to remain sane. Moments after he feels like he will to lose to the shield's influence, he is pulled back to sanity by Raphtalia. She receives severe burns due to her act, but does not regret helping him. At this point the Zombie Dragon has still not been defeated and is preparing for another attack, but it suddenly ceases moving while Filo bursts through it's chest with it's core in her mouth. With the corpse no longer moving Naofumi absorbs a mass of it into his shield and Filo eats a few pieces including part of it's core. Found in chapter 『Chapter 43』 of the web novel.