Crossover False Avatar? No, God Serena! (Fairy Tail x Avatar The Last Airbender)

After seemingly dying to Acnologia, God Serena finds himself in the world of Avatar that's embroiled in the Hundred War between the Fire Nation and the other countries called the Earth Kingdom, the Water Tribes and the dying Air Nomads. In this world, the Avatar was revered as a god with the power of four elements but had disappeared for a hundred years. Time to supplant the Avatar and become their new god who has the power of eight elements!