Riposte icon.
Riposte is a very rare defensive effect that causes the user to respond to attacks with a counterattack.
Effect
When a unit affected by Riposte is targeted by an attack, they will retaliate by attacking back to the original aggressor. The initial attack that targets the unit with Riposte does not need to inflict damage or hit: if it is dodged, Riposte will be triggered all the same. Nevertheless, a Riposte attack can be dodged as well. The attack that triggers Riposte can be melee or ranged and hit one or more targets, the only requirement is the unit with Riposte is targeted. Damage over time effects such as blight or bleeding will not trigger Riposte, but abilities that apply these statuses will, even if they don't inflict direct damage. However, Stress attacks which do not inflict damage will NOT trigger the Riposte (v.gr. the Madman's Accusation).
Riposte, unlike many status effects, lasts only for two turns; its duration can be refreshed by using the ability that activated it a second time.
A Riposte attack will have the base stats of the weapon held by the hero, inheriting damage and critical chance. Bear in mind, the Riposte will deal -40% base damage for the MAA and for the Highwayman progressively more damage as you level up his Duelist's Advance (from -40% to -15%).
Although you can increase the level of the skill that triggers the Riposte, the Riposte's base accuracy and critical chance will always remain the same, regardless of level of the skill. Unfortunately, that will implicate that at higher level's dungeons, opting to Riposte will become an even riskier gambit. This, however, can be mitigated with ACC increasing trinkets.
Synergies
By its nature, Riposte is extremely effective if paired with other effects (namely being marked) that draw the attention of the enemy: by being hit more, more Riposte counterattacks are carried out.
Notably, Riposte is a part of Retribution, one of the abilities of the Man-at-Arms, who also possesses Defender, a guard ability that redirects hits aimed to an ally to him, thus triggering Riposte while shielding the ally. This coupled with the increased PROT buff granted by this skill will allow the MAA to withstand increased amounts of punishment.
Though the Highwayman possesses no protection skill or marking that can be paired with his Riposte skill, the introduction of the Antiquarian and her Protect Me! skill synergizes extremely well with a hero's Riposte, meaning he will be counter-attacking more often while simultaneously being able to sponge up more damage and protecting the frail Antiquarian.