Counterblow

Counterblow – when the unit is attacked, it can make a defense roll even if it hasn’t declared Defense.
Counterblow

– Triggered ability
– When the creature with this ability is under the Melee Attack, it can declare its own Melee Attack with strength

afterward, if it’s still alive and within the distance of attack. All Critical effects could be activated following usual rules.
A creature cannot declare a Сounterblow in response to a Сounterblow.