Counter attack would be a skill a Black Knight could learn where an attack would take place before their "turn" in combat. IE:

Talen fiercly claws at your eyes.
Talen massacres you with his slash.
You decided its better to NOT parry with your empty hand.
Talen pounds you very hard.
Your counter attack massacres Talen!.
Talen pounds you.
Talen pounds you very hard.
Talen pounds you hard.
Your Counterattack massacres Talen!
Talen clambers on his feet.
You massacre Talen with your slash.

Open for ideas on how skill would actually work, I've got too much time on my hands at work sometimes

So if a counter attack occurred they wouldn't get one of their normal melee attacks during their combat round?

Actually, I was thinking those would be considered extra attacks, almost like fiery vortex; although not quite as deadly.

i was thinking mebbe counter attack wud work in such a way that a successful counter attack wud lead to the mob hitting itself instead of the bk.

How about counter attacks on stuff like kicks and headbutts, sorta like parry?