finalize_starting_relic_effect

finalize_starting_relic_effect = {
	# A holy site only has the three holy_relic_* slots, and a relic past that would sit unenshrined and assert on equip
	if = {
		limit = { scope:relic_site = { holy_site_artifact_count >= 3 } }
		destroy_artifact = scope:newly_created_artifact
	}
	else = {
		scope:newly_created_artifact = {
			scope:relic_owner = { save_scope_as = owner } # Required for the 'add_scaled_artifact_' scripted effects
			add_scaled_artifact_modifier_piety_effect = yes
			add_scaled_artifact_modifier_grandeur_small_effect = yes
			if = {
				limit = {
					OR = {
						rarity = famed
						rarity = illustrious
					}
				}
				add_2_scaled_artifact_modifier_devotion_effect = yes
			}
			else = {
				add_scaled_artifact_modifier_devotion_effect = yes
			}
			add_artifact_modifier = artifact_monthly_prestige_penalty_modifier # overwrite default creation modifier
		}

		scope:newly_created_artifact = {
			# Enshrine without history (setting owner & equipping = enshrining), skipping 'can_enshrine_artifact' rules)
			set_holy_site_owner = {
				target = scope:relic_site
				generate_history = no
			}
			equip_artifact_to_owner = yes
		}
	}
}

As written in game/common/scripted_effects/02_starting_holy_site_relics_effects.txt.