The target adds their fluency bonus to their feat roll against you in addition to any SNK bonuses (including proficiency and fluency) that they may have. They do not get this bonus if you speak their true name as a part of this ritual's incantation. The GM may also adjust the target's bonus up or down for other reasons at their discretion. If the target is aware that you are hunting them, they make their roll with advantage.
Note: The only part of this ability that modifies duels is that the battle is a "fight to the death". If Active Bow Out is used on Undead Hunter, this merely becomes a normal duel.