tribal_challenger_lost_effect

tribal_challenger_lost_effect = {
	if = {
		limit = {
			root = scope:liege_to_challenge
		}
		scope:liege_to_challenge = {
			add_prestige = medium_prestige_gain
		}
	}
	else = {
		hidden_effect = {
			scope:liege_to_challenge = {
				add_prestige = medium_prestige_gain
			}
		}
	}
	add_prestige_level = -1
	if = {
		limit = {
			root = scope:challenger
		}
		scope:liege_to_challenge = {
			add_opinion = {
				target = scope:challenger
				modifier = tried_to_usurped_title
			}
		}
	}
	else = {
		hidden_effect = {
			scope:liege_to_challenge = {
				add_opinion = {
					target = scope:challenger
					modifier = tried_to_usurped_title
				}
			}
		}
	}
}

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