maiming_destroy_diarchy_effect

maiming_destroy_diarchy_effect = {
	if = {
		limit = { exists = scope:destroy_diarchy }
		# Liege maims co-emperor.
		if = {
			limit = { scope:actor.diarch = scope:recipient }
			scope:actor = {
				clear_designated_heir = yes
				end_diarchy = yes
			}
			every_player = {
				limit = {
					NOR = {
						this = scope:actor
						this = scope:recipient
					}
					top_liege = scope:actor.top_liege
				}
				trigger_event = diarchy.8022
			}
		}
		# Co-emperor maims liege.
		else = {
			# We do this in two batches so that we don't produce an error when the emperor is usurped by their old co-emperor.
			## First the empire.
			create_title_and_vassal_change = {
				type = usurped
				save_scope_as = change
			}
			scope:recipient = {
				every_held_title = {
					limit = {
						OR = {
							this = scope:recipient.capital_county
							this = scope:recipient.capital_county.duchy
							AND = {
								tier = tier_county
								this.duchy = scope:recipient.capital_county.duchy
							}
							tier >= scope:recipient.highest_held_title_tier
						}
					}
					change_title_holder = {
						holder = scope:actor
						change = scope:change
					}
				}
				every_vassal = {
					custom = custom.recipient_every_vassal
					change_liege = {
						LIEGE = scope:actor
						CHANGE = scope:change
					}
				}
			}
			resolve_title_and_vassal_change = scope:change
			## Then the former emperor.
			create_title_and_vassal_change = {
				type = usurped
				save_scope_as = change2
			}
			scope:recipient = {
				change_liege = {
					LIEGE = scope:actor
					CHANGE = scope:change2
				}
			}
			resolve_title_and_vassal_change = scope:change2
			# Plus, end the diarchy.
			hidden_effect = {
				scope:recipient = { end_diarchy = yes }
			}
			every_player = {
				limit = {
					NOR = {
						this = scope:actor
						this = scope:recipient
					}
					top_liege = scope:actor.top_liege
				}
				trigger_event = diarchy.8023
			}
		}
	}
}

As written in game/common/scripted_effects/00_diarchy_scripted_effects.txt.