its an enchantment that gives your first attack of the round pierce +3. Its a promo that came out a long time ago. I'm guessing around the time of forcelord versus Warmaster.
I would rather that it work as an opposite to the Veteran's Belt. What i mean is that the first attack of a round, it turns 2 normal damage into critical damage.
The old critical strike is better with big attacks(lots of normal damage) against opponents which have a fair amount of armor. It is bad with smaller attacks against high armor opponents because that piercing doesnt remove enough armor to get any normal damage through. With brace yourself it is now trivial to get even small creatures up to 5 armor.
I guess what i am saying is that if critical strike ever becomes more than a promo, I think it would be more fun my way as a reverse Veteran's Belt.