Read in the patch notes that Manifestations for Tzeentch got buffed, but maybe too much. Started a campaign as Yuan Bo and the nearby Tzeentch faction declared war, they keep hitting my armies with mutagenic energies attrition and that ability essensially kills the entire army in 3 turns no matter what and lasts for longer then that. I don't mind a challange, but i feel like this is a bit of a too powerfull ability for the AI to be able to use.