Long ago, Zotz was locked away after attempting to take over Drayma the first time. After hundreds of Drayma Years, Zotz the mewtwo escaped and flew to Drayma from Kahli island with a giant army of evil pokemon that he calls "Death Clan."
This army had even the power to harm Spirit Clan, Death Clan's opposite. Spirit Clan is like Heaven, while Death Clan (Or the Underworld) is like Hell.
First, Death Clan took over most of the areas in Drayma when suddenly more were discovered and Death Clan lost power.
Sixteen chosen pokemon, four from each Clan, were led by Shade the Umbreon, leader of Rath Clan.
First they organized a meeting with Zotz at Yueto Riverside, then they met him again two days later and used a spell to destroy him forever.
After that, Death Clan was scared back to Kahli when all of them suddenly were killed by Spirit Clan, and they were all reincarnated as productive members of society, the only way to completely destroy a spirit.
Zotz was reincarnated in one of Kasui and Mistuko's children, a cross between a Mew and a Nidoran Male. He does not remember his past self, however, and never will.