Wild is a boar-like creature trapped in Purgatory, best known for his obsessive search for his younger brother, Mild—also called Hawk. Born in Purgatory itself, Wild once cared for Mild and would sing him lullabies, but the Demon King kidnapped the child shortly after birth and dragged him to another world. For millions of years, Wild has hunted for his brother while repeatedly clashing with the Demon King, though he's consistently come up short in those fights.
Everything changed when Wild ran into Meliodas and Ban in Purgatory. Recognizing a real chance to finally take down the Demon King and escape his eternal prison, he threw in with them. Defeating the Demon King became the key to getting out—and hopefully finding Mild at last.
Content compiled by AnimeList.moe from publicly available sources.
