relic_war_valid_against_defender_vassal_trigger

relic_war_valid_against_defender_vassal_trigger = {
	any_vassal_or_below = {
		faith != scope:attacker.faith
		any_character_artifact = {
			OR = {
				# Standard holy relics.
				AND = {
					is_holy_relic_for = scope:attacker.faith
					NOT = {
						is_holy_relic_for = scope:defender.faith
					}
				}
				# Struggle relics.
				## The Bells of Santiago de Compostela.
				AND = {
					exists = var:relic
					var:relic = flag:iberian_struggle
					scope:attacker = {
						any_character_struggle = { is_struggle_type = iberian_struggle }
						# Plus one of the valid using faiths.
						OR = {
							scope:attacker = {
								islamic_artifact_access_trigger = yes
							}
							scope:attacker = {
								christian_artifact_access_trigger = yes
							}
						}
					}
					scope:attacker.faith != scope:defender.faith
				}
			}
		}
	}
}

As written in game/common/scripted_triggers/00_artifact_triggers.txt.