Kari was part of a ritual sacrifice to god, for some reason this ended up giving him magic powers and also turned his entire village into zombies, he then spent the next 50 years making the Zomviguarna as part of a search to make himself immortal, but never succeeded
at some point he turned fonido into his base, and after Nat's parents were killed the Margarette doll ended up with him, seeking company he turned it into a Zomviguarna, however Maggie retained her memories of Nat and wanted to see him, heartbroken Kari ripped her apart and dumped her in a nearby forest which coincidently is also right next to Victor's mansion where Nat then found her and put her back together