RIPOSTE: This unit has a set chance to inflict damage to any melee attacker that attacks it.
*Applies to normal, melee attacks, double attacks, triple attacks, quadra attacks, and penta attacks. Each separate attack has a chance to proc this ability.
So after using Riposte in this GB, the damage happens simultaneously between the melee attacker and the unit with Riposte.
Multi-attacks have a chance to trigger Riposte on each hit - so it's theoretically possible to hit back for each hit of a Double/Triple/Quad/Penta melee attack (Payne can kill Charles with two Riposte strikes depending on deployment, btw.)
This also arguably means that the 15DC 7* with Riposte, LUDA
is not only bonkers, but the fact that she's a mage is almost irrelevant as long as the attacking force is melee.