The character lashes out with the shield three times. All hits are critical hits. If the last strike connects, the target is knocked down unless it passes a physical resistance check vs the attacker's strength attribute.
If the target is knocked down, they are also dazed for 10 seconds, reducing attack and defence by 5.
Shield Mastery causes all damage rolls to be maximized (highest roll on the weapon's damage range). However, due to inconsistencies in their implementation, shields have a base damage of 5 and 'maximum' damage of 0, which results in Shield Mastery actually causing the damage to be reduced.
Conjuration time: 1s.
100 additional Threat is supposed to be drawn from the target. As of Patch 1.02, only damage-based Threat is drawn.
Activation base is in Stamina and values vary with fatigue%.
The tooltip is incorrect. All three hits are criticals.
It’s worthy to note the amazing synergy Overpower has with Cone of Cold/Petrify: as of patch 1.05, to the contrary to what the combat mechanics page seems to claim, it is possible to shatter lieutenant-ranked creatures, as demonstrated in this video. The chance of shattering a lieutenant creature on Nightmare difficulty is 5%. Now, Overpower generates three quick auto-crits into the same target, out of which, at least one needs to succeed. Consequently, the overall chance to shatter a lieutenant enemy on Nightmare difficulty with Overpower is 14.26%.