Frenzy is an ability such that, upon success to damage an enemy via normal attack, the unit processing Frenzy will Attack Plus X. The attack increase is stackable. It is dependant on physical defense, such that if damage is totally blocked the ability will not be triggered.
Frenzy is generally weak against ability damage, Block and Flying units, as most of the frenzy units have 1 attack, cannot fight flying units and are not with enough health restoring abilities. Thus it is advised to partner frenzy units with Heal, Regenerate, and Archery. An unusual combination of Frenzy with Whirlwind, Drain and Flying can be used but the associated artifacts (War Brew, Soul Leech, Bows, Skarg's Axe) are very hard to obtain.