The Seven Deadly Sins: Four Knights of the Apocalypse Episode 4 English Dubbed Episode Title: The Demon of Echo Gorge Episode Description: Under Nasiens' captivity, Percival learns that Nasiens is developing an antidote for the poisonous miasma plaguing Echo Gorge, with the animals' mutations being an unintended side effect of his experiments. Deciding to trust Nasiens, Percival willingly drinks the untested drug despite its potentially lethal effects, proving it to be a success. After Percival convinces the fairies of Nasiens' innocence, Nasiens spreads the drug across the gorge and restores it to its original state through his magic ability, Mix Venom. However, the gorge is poisoned again by Ordo, Nasiens' long-lost mentor and adoptive grandfather, who has been transformed into a monster under the control of the fairy creature whom Nasiens imprisoned earlier. Realizing Ordo is the true source of the miasma, Percival promises to return Ordo to normal.