pam_heresy_pick_epicenter_ruler_effect

pam_heresy_pick_epicenter_ruler_effect = {
	clear_saved_scope = epicenter_ruler

	# Strict: try the historical capital's holder first.
	if = {
		limit = {
			pam_heresy_strict_rule_trigger = yes
			exists = scope:heresy_strict_capital
			scope:heresy_strict_capital.holder ?= {
				faith = root
				is_landed = yes
				is_ai = yes
				highest_held_title_tier >= tier_duchy
				NOR = {
					this = root.religious_head
					has_trait = heresiarch
					has_trait = herald
					recently_converted_faith_trigger = yes
				}
			}
		}
		scope:heresy_strict_capital.holder = { save_scope_as = epicenter_ruler }
	}

	# Default / fallback: regional duke+ holder.
	if = {
		limit = { NOT = { exists = scope:epicenter_ruler } }
		random_faith_ruler = {
			limit = {
				is_eligible_heresy_epicenter_ruler_trigger = yes
				OR = {
					pam_heresy_relaxed_rule_trigger = yes
					AND = {
						# Default: must be in heresy region.
						pam_heresy_default_rule_trigger = yes
						exists = capital_county
						capital_county.title_province = {
							pam_heresy_capital_in_heresy_region_trigger = yes
						}
					}
					AND = {
						# Strict but historical capital not held by an eligible ruler:
						# fall back to default-region behaviour rather than skipping.
						pam_heresy_strict_rule_trigger = yes
						exists = capital_county
						capital_county.title_province = {
							pam_heresy_capital_in_heresy_region_trigger = yes
						}
					}
				}
			}
			weight = {
				base = 100
				modifier = {
					factor = 2
					highest_held_title_tier >= tier_kingdom
				}
				modifier = {
					factor = 1.5
					OR = {
						has_trait = zealous
						has_trait = lifestyle_mystic
						has_trait = lifestyle_scholar
						has_trait = theologian
					}
				}
				modifier = {
					factor = 0.5
					opinion = {
						target = root.religious_head
						value >= 75
					}
				}
			}
			save_scope_as = epicenter_ruler
		}
	}
}

As written in game/common/scripted_effects/pam_heresy_shared_effects.txt.