decrease_house_relation_level_effect

decrease_house_relation_level_effect = {
	save_scope_as = house
	$HOUSE$ ?= { save_scope_as = other_house }
	scope:house ?= {
		if = {
			limit = {
				exists = scope:other_house
				scope:other_house != this
			}
			if = {
				limit = { has_house_relation_with = scope:other_house }
				random_house_relation = {
					limit = {
						any_relation_house = { scope:other_house = this }
					}
					save_scope_as = house_relation
					if = {
						limit = { has_house_relation_level = amity }
						scope:house = {
							set_house_relation_level_effect = {
								HOUSE = scope:other_house
								REASON = $REASON$
								LEVEL = friendly
							}
						}
					}
					else_if = {
						limit = { has_house_relation_level = friendly }
						scope:house = {
							set_house_relation_level_effect = {
								HOUSE = scope:other_house
								REASON = $REASON$
								LEVEL = cordial
							}
						}
					}
					else_if = {
						limit = { has_house_relation_level = cordial }
						scope:house = {
							set_house_relation_level_effect = {
								HOUSE = scope:other_house
								REASON = $REASON$
								LEVEL = neutral
							}
						}
					}
					else_if = {
						limit = { has_house_relation_level = neutral }
						scope:house = {
							set_house_relation_level_effect = {
								HOUSE = scope:other_house
								REASON = $REASON$
								LEVEL = quarrel
							}
						}
					}
					else_if = {
						limit = { has_house_relation_level = quarrel }
						scope:house = {
							set_house_relation_level_effect = {
								HOUSE = scope:other_house
								REASON = $REASON$
								LEVEL = rivalry
							}
						}
					}
					else_if = {
						limit = { has_house_relation_level = rivalry }
						scope:house = {
							set_house_relation_level_effect = {
								HOUSE = scope:other_house
								REASON = $REASON$
								LEVEL = feud
							}
						}
					}
				}
			}
			else = {
				set_house_relation_level_effect = {
					HOUSE = scope:other_house
					REASON = $REASON$
					LEVEL = quarrel
				}
				random_house_relation = {
					limit = { any_relation_house = { this = scope:other_house } }
					save_scope_as = house_relation
				}
			}
		}
	}
}

As written in game/common/scripted_effects/10_dlc_tgp_house_relation_scripted_effects.txt.